Revert "[Buildbucket] Validate gerrit changelist hostnames."

This reverts commit bb21c01819ebd9788ee4034d523d0996e9af2c21.

Reason for revert: Let's roll this back until builders produce valid data; Otherwise Buildbucket is undeployable.

Original change's description:
> [Buildbucket] Validate gerrit changelist hostnames.
>
> Stop accepting invalid gerrit changelists in builds.
> This is causing problems downstream in LUCI Analysis.
>
> BUG=b:261350048
> TEST=Integration tests
>
> Change-Id: Ide0065000913509dab08be8e37fcd4f1b3ce68cd
> Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/4075220
> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
> Commit-Queue: Patrick Meiring <meiring@google.com>

Bug: b:261350048
Change-Id: Id619e48aa9b51576be6dc120115177f2a3a7bf63
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/4087520
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Robbie Iannucci <iannucci@chromium.org>
diff --git a/buildbucket/appengine/rpc/schedule_build.go b/buildbucket/appengine/rpc/schedule_build.go
index dc0e9c6..6ed9ff7 100644
--- a/buildbucket/appengine/rpc/schedule_build.go
+++ b/buildbucket/appengine/rpc/schedule_build.go
@@ -49,11 +49,6 @@
 	"go.chromium.org/luci/buildbucket/protoutil"
 )
 
-// Allow hostnames permitted by
-// https://www.rfc-editor.org/rfc/rfc1123#page-13. (Note that
-// the 255 character limit must be seperately applied.)
-var hostnameRE = regexp.MustCompile(`^[a-z0-9][a-z0-9-]+(\.[a-z0-9-]+)*$`)
-
 func min(i, j int) int {
 	if i < j {
 		return i
@@ -120,10 +115,6 @@
 		return errors.Reason("change must be specified").Err()
 	case ch.Host == "":
 		return errors.Reason("host must be specified").Err()
-	case !hostnameRE.MatchString(ch.Host):
-		return errors.Reason("host does not match pattern %q", hostnameRE).Err()
-	case len(ch.Host) > 255:
-		return errors.Reason("host must not exceed 255 characters").Err()
 	case ch.Patchset == 0:
 		return errors.Reason("patchset must be specified").Err()
 	case ch.Project == "":
diff --git a/buildbucket/appengine/rpc/schedule_build_test.go b/buildbucket/appengine/rpc/schedule_build_test.go
index 9a7ab94..fdba035 100644
--- a/buildbucket/appengine/rpc/schedule_build_test.go
+++ b/buildbucket/appengine/rpc/schedule_build_test.go
@@ -19,7 +19,6 @@
 	"encoding/base64"
 	"math/rand"
 	"strconv"
-	"strings"
 	"testing"
 	"time"
 
@@ -6198,50 +6197,18 @@
 			})
 
 			Convey("host", func() {
-				Convey("not specified", func() {
-					req := &pb.ScheduleBuildRequest{
-						GerritChanges: []*pb.GerritChange{
-							{
-								Change:   1,
-								Patchset: 1,
-								Project:  "project",
-							},
+				req := &pb.ScheduleBuildRequest{
+					GerritChanges: []*pb.GerritChange{
+						{
+							Change:   1,
+							Patchset: 1,
+							Project:  "project",
 						},
-						TemplateBuildId: 1,
-					}
-					err := validateSchedule(req, nil, nil)
-					So(err, ShouldErrLike, "host must be specified")
-				})
-				Convey("invalid", func() {
-					req := &pb.ScheduleBuildRequest{
-						GerritChanges: []*pb.GerritChange{
-							{
-								Change:   1,
-								Host:     "https://somehost", // host should not include the protocol.
-								Patchset: 1,
-								Project:  "project",
-							},
-						},
-						TemplateBuildId: 1,
-					}
-					err := validateSchedule(req, nil, nil)
-					So(err, ShouldErrLike, "host does not match pattern")
-				})
-				Convey("too long", func() {
-					req := &pb.ScheduleBuildRequest{
-						GerritChanges: []*pb.GerritChange{
-							{
-								Change:   1,
-								Host:     strings.Repeat("h", 256),
-								Patchset: 1,
-								Project:  "project",
-							},
-						},
-						TemplateBuildId: 1,
-					}
-					err := validateSchedule(req, nil, nil)
-					So(err, ShouldErrLike, "host must not exceed 255 characters")
-				})
+					},
+					TemplateBuildId: 1,
+				}
+				err := validateSchedule(req, nil, nil)
+				So(err, ShouldErrLike, "host must be specified")
 			})
 
 			Convey("patchset", func() {