Replace setTimeout with step_timeout in inert/ tests (#18541)

This avoids the need to silence the lint.
diff --git a/inert/inert-retargeting-iframe.tentative.html b/inert/inert-retargeting-iframe.tentative.html
index c31cc88..ddcb3cc 100644
--- a/inert/inert-retargeting-iframe.tentative.html
+++ b/inert/inert-retargeting-iframe.tentative.html
@@ -158,7 +158,7 @@
         }
         element.addEventListener(event, f, { capture: true, once: true });
 
-        setTimeout(() => {
+        step_timeout(() => {
           element.removeEventListener(event, f, { capture: true });
           reject("did not get " + event + " on " + element.id);
         }, 1000);
@@ -181,7 +181,7 @@
         }
         element.addEventListener(event, f, { capture: true, once: true });
 
-        setTimeout(() => {
+        step_timeout(() => {
           element.removeEventListener(event, f, { capture: true });
           resolve();
         }, 1000);
diff --git a/inert/inert-retargeting.tentative.html b/inert/inert-retargeting.tentative.html
index 6ef3b2a..2280cf5 100644
--- a/inert/inert-retargeting.tentative.html
+++ b/inert/inert-retargeting.tentative.html
@@ -159,7 +159,7 @@
         }
         element.addEventListener(event, f, { capture: true, once: true });
 
-        setTimeout(() => {
+        step_timeout(() => {
           element.removeEventListener(event, f, { capture: true });
           reject("did not get " + event + " on " + element.id);
         }, 1000);
@@ -182,7 +182,7 @@
         }
         element.addEventListener(event, f, { capture: true, once: true });
 
-        setTimeout(() => {
+        step_timeout(() => {
           element.removeEventListener(event, f, { capture: true });
           resolve();
         }, 1000);
diff --git a/lint.whitelist b/lint.whitelist
index a6aa946..8ff3b81 100644
--- a/lint.whitelist
+++ b/lint.whitelist
@@ -820,9 +820,6 @@
 WEB-PLATFORM.TEST:signed-exchange/appcache/resources/*.sxg
 WEB-PLATFORM.TEST:signed-exchange/resources/generate-test-sxgs.sh
 
-SET TIMEOUT: inert/inert-retargeting.tentative.html
-SET TIMEOUT: inert/inert-retargeting-iframe.tentative.html
-
 # https://github.com/web-platform-tests/wpt/issues/16455
 MISSING DEPENDENCY: idle-detection/interceptor.https.html
 MISSING DEPENDENCY: sms/sms_provider.js