Revert "[import-attributes] Disable flag for import assertions"

This reverts commit fc0cd5fd4ecb855b374770ed437b0aea040d2cb4.

Reason for revert: Caused failures on https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Blink%20Linux/30618/overview

Original change's description:
> [import-attributes] Disable flag for import assertions
>
> The 'assert' syntax has been deprecated for 3 milestones with a warning
> message saying it will removed in 12.6.
>
> This CL disables the flag by default without removing any code, pending
> evidence of web compatibility.
>
> See https://groups.google.com/a/chromium.org/g/blink-dev/c/ZHvzLaJZRvo/m/FgNDBjrtBQAJ
>
> Bug: 40643756
> Change-Id: Ieed38216f62bc2c0791a22bee181913338e451bf
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5508153
> Commit-Queue: Shu-yu Guo <syg@chromium.org>
> Reviewed-by: Rezvan Mahdavi Hezaveh <rezvan@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#93706}

Bug: 40643756
Change-Id: I43e3d0b35cb7239146900b9ebe3844a5b778faef
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5516098
Owners-Override: Rezvan Mahdavi Hezaveh <rezvan@chromium.org>
Auto-Submit: Rezvan Mahdavi Hezaveh <rezvan@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Rezvan Mahdavi Hezaveh <rezvan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#93710}
diff --git a/src/flags/flag-definitions.h b/src/flags/flag-definitions.h
index 76d82c2..31501c5 100644
--- a/src/flags/flag-definitions.h
+++ b/src/flags/flag-definitions.h
@@ -242,8 +242,7 @@
     "harmony weak references with FinalizationRegistry.prototype.cleanupSome") \
   V(harmony_temporal, "Temporal")                                              \
   V(harmony_shadow_realm, "harmony ShadowRealm")                               \
-  V(harmony_struct, "harmony structs, shared structs, and shared arrays")      \
-  V(harmony_import_assertions, "harmony import assertions (deprecated)")
+  V(harmony_struct, "harmony structs, shared structs, and shared arrays")
 
 #define JAVASCRIPT_INPROGRESS_FEATURES_BASE(V)                       \
   V(js_explicit_resource_management, "explicit resource management") \
@@ -284,6 +283,7 @@
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING_BASE(V)                                      \
+  V(harmony_import_assertions, "harmony import assertions")           \
   V(harmony_rab_gsab,                                                 \
     "harmony ResizableArrayBuffer / GrowableSharedArrayBuffer")       \
   V(harmony_rab_gsab_transfer, "harmony ArrayBuffer.transfer")        \
diff --git a/test/mjsunit/harmony/modules-import-attributes-3.mjs b/test/mjsunit/harmony/modules-import-attributes-3.mjs
index 385c72d..34db185 100644
--- a/test/mjsunit/harmony/modules-import-attributes-3.mjs
+++ b/test/mjsunit/harmony/modules-import-attributes-3.mjs
@@ -4,6 +4,6 @@
 
 // Flags: --harmony-import-attributes
 
-import {life} from 'modules-skip-imports-attributes-json-1.mjs';
+import {life} from 'modules-skip-imports-json-1.mjs';
 
 assertEquals(42, life());
diff --git a/test/mjsunit/harmony/modules-import-attributes-dynamic-5.mjs b/test/mjsunit/harmony/modules-import-attributes-dynamic-5.mjs
index 34c7e39..cdb1567 100644
--- a/test/mjsunit/harmony/modules-import-attributes-dynamic-5.mjs
+++ b/test/mjsunit/harmony/modules-import-attributes-dynamic-5.mjs
@@ -5,7 +5,7 @@
 // Flags: --allow-natives-syntax --harmony-import-attributes
 
 var life;
-import('modules-skip-imports-attributes-json-1.mjs',).then(namespace => life = namespace.life());
+import('modules-skip-imports-json-1.mjs',).then(namespace => life = namespace.life());
 
 %PerformMicrotaskCheckpoint();
 
diff --git a/test/mjsunit/harmony/modules-skip-imports-attributes-json-1.mjs b/test/mjsunit/harmony/modules-skip-imports-attributes-json-1.mjs
deleted file mode 100644
index 4ab4653..0000000
--- a/test/mjsunit/harmony/modules-skip-imports-attributes-json-1.mjs
+++ /dev/null
@@ -1,8 +0,0 @@
-// Copyright 2021 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Flags: --harmony-import-attributes
-
-import json from "modules-skip-1.json" with { type: "json" };
-export function life() { return json.life; }
diff --git a/test/mjsunit/harmony/modules-skip-imports-json-1.mjs b/test/mjsunit/harmony/modules-skip-imports-json-1.mjs
index 63474b8..3930313d 100644
--- a/test/mjsunit/harmony/modules-skip-imports-json-1.mjs
+++ b/test/mjsunit/harmony/modules-skip-imports-json-1.mjs
@@ -2,7 +2,5 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-import-assertions
-
 import json from "modules-skip-1.json" assert { type: "json" };
 export function life() { return json.life; }