Remove feature flag removeListenersOnDetach

Summary:
changelog: [internal]

Remove unused feature flag.

Reviewed By: yungsters

Differential Revision: D41188496

fbshipit-source-id: 13507197e7943aea9303ffb828feddb77c94ab0c

Libraries/Animated/nodes/AnimatedNode.js

@@ -30,9 +30,7 @@ export default class AnimatedNode {
   __nativeAnimatedValueListener: ?any;
   __attach(): void {}
   __detach(): void {
-    if (ReactNativeFeatureFlags.removeListenersOnDetach()) {
-      this.removeAllListeners();
-    }
+    this.removeAllListeners();
     if (this.__isNative && this.__nativeTag != null) {
       NativeAnimatedHelper.API.dropAnimatedNode(this.__nativeTag);
       this.__nativeTag = undefined;

Libraries/ReactNative/ReactNativeFeatureFlags.js

@@ -43,8 +43,6 @@ export type FeatureFlags = {|
    * to render react components driven by classes written in C++.
    */
   enableCppRenderSystem: () => boolean,
-
-  removeListenersOnDetach: () => boolean,
 |};
 
 const ReactNativeFeatureFlags: FeatureFlags = {
@@ -54,7 +52,6 @@ const ReactNativeFeatureFlags: FeatureFlags = {
   animatedShouldDebounceQueueFlush: () => false,
   animatedShouldUseSingleOp: () => false,
   enableCppRenderSystem: () => false,
-  removeListenersOnDetach: () => false,
 };
 
 module.exports = ReactNativeFeatureFlags;