Remove feature flag for rebase whole chain

Rollout to 100% happened already a 2 weeks ago.

Release-Notes: User can rebase whole chain from UI.
Google-Bug-Id: b/246166556
Change-Id: I0c78a45447606231affe53da2b332f15baf662c8
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts
index c2739f3..ad2ba8f 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts
@@ -22,7 +22,6 @@
 import {sharedStyles} from '../../../styles/shared-styles';
 import {ValueChangedEvent} from '../../../types/events';
 import {throwingErrorCallback} from '../../shared/gr-rest-api-interface/gr-rest-apis/gr-rest-api-helper';
-import {KnownExperimentId} from '../../../services/flags/flags';
 
 export interface RebaseChange {
   name: string;
@@ -99,8 +98,6 @@
 
   private readonly restApiService = getAppContext().restApiService;
 
-  private readonly flagsService = getAppContext().flagsService;
-
   constructor() {
     super();
     this.query = input => this.getChangeSuggestions(input);
@@ -234,8 +231,7 @@
             >
           </div>
           ${when(
-            this.flagsService.isEnabled(KnownExperimentId.REBASE_CHAIN) &&
-              this.hasParent,
+            this.hasParent,
             () =>
               html`<div>
                 <input
diff --git a/polygerrit-ui/app/services/flags/flags.ts b/polygerrit-ui/app/services/flags/flags.ts
index 29e9259..7488e79 100644
--- a/polygerrit-ui/app/services/flags/flags.ts
+++ b/polygerrit-ui/app/services/flags/flags.ts
@@ -19,5 +19,4 @@
   PUSH_NOTIFICATIONS_DEVELOPER = 'UiFeature__push_notifications_developer',
   PUSH_NOTIFICATIONS = 'UiFeature__push_notifications',
   SUGGEST_EDIT = 'UiFeature__suggest_edit',
-  REBASE_CHAIN = 'UiFeature__rebase_chain',
 }