address comments

src/objective-c/GRPCClient/GRPCCall.m

@@ -425,9 +425,6 @@ const char *kCFStreamVarName = "grpc_cfstream";
   // queue
   dispatch_queue_t _responseQueue;
 
-  // Whether the call is finished. If it is, should not call finishWithError again.
-  BOOL _finished;
-
   // The OAuth2 token fetched from a token provider.
   NSString *_fetchedOauth2AccessToken;
 }
@@ -750,7 +747,6 @@ const char *kCFStreamVarName = "grpc_cfstream";
     [self cancel];
   } else {
     dispatch_async(_callQueue, ^{
-
       // EOS error is not processed here. It is handled by op batch of GRPC_OP_RECV_STATUS_ON_CLIENT
       [self finishRequestWithErrorHandler:nil];
     });

src/objective-c/RxLibrary/GRXConcurrentWriteable.m

@@ -113,10 +113,8 @@
 
 - (void)cancelSilently {
   dispatch_async(_writeableQueue, ^{
-    @synchronized(self) {
-      if (self->_alreadyFinished) {
-        return;
-      }
+    if (self->_alreadyFinished) {
+      return;
     }
     self.writeable = nil;
   });

src/objective-c/RxLibrary/GRXWriter.h

@@ -82,7 +82,7 @@ typedef NS_ENUM(NSInteger, GRXWriterState) {
  * the corresponding value, and that's useful for advanced use cases like pausing an writer. For
  * more details, see the documentation of the enum further down. The property is thread safe.
  */
-@property(atomic) GRXWriterState state;
+@property GRXWriterState state;
 
 /**
  * Transition to the Started state, and start sending messages to the writeable (a reference to it