fix(material/tabs): remove IE animation workaround (angular#29899)

Removes a workaround that's no longer necessary now that we don't support IE.

Author: crisbeto

src/material/tabs/tab-body.ts

@@ -26,7 +26,7 @@ import {
   inject,
 } from '@angular/core';
 import {Subject, Subscription} from 'rxjs';
-import {distinctUntilChanged, startWith} from 'rxjs/operators';
+import {startWith} from 'rxjs/operators';
 import {matTabsAnimations} from './tabs-animations';
 
 /**
@@ -174,24 +174,16 @@ export class MatTabBody implements OnInit, OnDestroy {
       });
     }
 
-    // Ensure that we get unique animation events, because the `.done` callback can get
-    // invoked twice in some browsers. See https://github.com/angular/angular/issues/24084.
-    this._translateTabComplete
-      .pipe(
-        distinctUntilChanged((x, y) => {
-          return x.fromState === y.fromState && x.toState === y.toState;
-        }),
-      )
-      .subscribe(event => {
-        // If the transition to the center is complete, emit an event.
-        if (this._isCenterPosition(event.toState) && this._isCenterPosition(this._position)) {
-          this._onCentered.emit();
-        }
+    this._translateTabComplete.subscribe(event => {
+      // If the transition to the center is complete, emit an event.
+      if (this._isCenterPosition(event.toState) && this._isCenterPosition(this._position)) {
+        this._onCentered.emit();
+      }
 
-        if (this._isCenterPosition(event.fromState) && !this._isCenterPosition(this._position)) {
-          this._afterLeavingCenter.emit();
-        }
-      });
+      if (this._isCenterPosition(event.fromState) && !this._isCenterPosition(this._position)) {
+        this._afterLeavingCenter.emit();
+      }
+    });
   }
 
   /**