[App Check] Always return fresh limitedUseToken

Potential fix for #11270 (comment)

Author: andrewheard

FirebaseAppCheck/Sources/Core/FIRAppCheck.m

@@ -72,7 +72,6 @@ @interface FIRAppCheck () <FIRAppCheckInterop>
 @property(nonatomic, readonly, nullable) id<FIRAppCheckTokenRefresherProtocol> tokenRefresher;
 
 @property(nonatomic, nullable) FBLPromise<FIRAppCheckToken *> *ongoingRetrieveOrRefreshTokenPromise;
-@property(nonatomic, nullable) FBLPromise<FIRAppCheckToken *> *ongoingLimitedUseTokenPromise;
 @end
 
 @implementation FIRAppCheck
@@ -180,7 +179,7 @@ - (void)tokenForcingRefresh:(BOOL)forcingRefresh
 
 - (void)limitedUseTokenWithCompletion:(void (^)(FIRAppCheckToken *_Nullable token,
                                                 NSError *_Nullable error))handler {
-  [self retrieveLimitedUseToken]
+  [self limitedUseToken]
       .then(^id _Nullable(FIRAppCheckToken *token) {
         handler(token, nil);
         return token;
@@ -314,26 +313,6 @@ - (nonnull NSString *)notificationTokenKey {
   });
 }
 
-- (FBLPromise<FIRAppCheckToken *> *)retrieveLimitedUseToken {
-  return [FBLPromise do:^id _Nullable {
-    if (self.ongoingLimitedUseTokenPromise == nil) {
-      // Kick off a new operation only when there is not an ongoing one.
-      self.ongoingLimitedUseTokenPromise =
-          [self limitedUseToken]
-              // Release the ongoing operation promise on completion.
-              .then(^FIRAppCheckToken *(FIRAppCheckToken *token) {
-                self.ongoingLimitedUseTokenPromise = nil;
-                return token;
-              })
-              .recover(^NSError *(NSError *error) {
-                self.ongoingLimitedUseTokenPromise = nil;
-                return error;
-              });
-    }
-    return self.ongoingLimitedUseTokenPromise;
-  }];
-}
-
 - (FBLPromise<FIRAppCheckToken *> *)refreshToken {
   return [FBLPromise
              wrapObjectOrErrorCompletion:^(FBLPromiseObjectOrErrorCompletion _Nonnull handler) {