Remove __block for synchronized blocks

src/objective-c/GRPCClient/GRPCCall.m

@@ -564,7 +564,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
   }
 
   NSMutableDictionary *headers = _requestHeaders;
-  __block NSString *fetchedOauth2AccessToken;
+  NSString *fetchedOauth2AccessToken;
   @synchronized(self) {
     fetchedOauth2AccessToken = _fetchedOauth2AccessToken;
   }

src/objective-c/GRPCClient/private/GRPCChannelPool.m

@@ -190,7 +190,7 @@ extern const char *kCFStreamVarName;
 }
 
 - (GRPCChannel *)channelWithConfiguration:(GRPCChannelConfiguration *)configuration {
-  __block GRPCChannel *channel;
+  GRPCChannel *channel;
   @synchronized(self) {
     if ([_channelPool objectForKey:configuration]) {
       channel = _channelPool[configuration];

src/objective-c/GRPCClient/private/GRPCHost.m

@@ -141,7 +141,7 @@ static NSMutableDictionary *gHostCache;
     host = [hostURL.host stringByAppendingString:@":443"];
   }
 
-  __block GRPCCallOptions *callOptions = nil;
+  GRPCCallOptions *callOptions = nil;
   @synchronized(gHostCache) {
     if ([gHostCache objectForKey:host]) {
       callOptions = [gHostCache[host] callOptions];