some nit fixes

src/objective-c/GRPCClient/GRPCCall.m

@@ -282,7 +282,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
 
 - (void)issueClosedWithTrailingMetadata:(NSDictionary *)trailingMetadata error:(NSError *)error {
   if ([_handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
-    [_handler closedWithTrailingMetadata:_call.responseTrailers error:error];
+    [_handler closedWithTrailingMetadata:trailingMetadata error:error];
   }
 }
 

src/objective-c/GRPCClient/GRPCCallOptions.m

@@ -45,7 +45,7 @@ static NSString *const kDefaultChannelPoolDomain = nil;
 static const NSUInteger kDefaultChannelID = 0;
 
 // Check if two objects are equal. Returns YES if both are nil;
-BOOL areObjectsEqual(id obj1, id obj2) {
+static BOOL areObjectsEqual(id obj1, id obj2) {
   if (obj1 == obj2) {
     return YES;
   }

src/objective-c/GRPCClient/private/GRPCChannel.h

@@ -39,7 +39,7 @@ NS_ASSUME_NONNULL_BEGIN
  * Options of the corresponding call. Note that only the channel-related options are of interest to
  * this class.
  */
-@property(strong, readonly) GRPCCallOptions *callOptions;
+@property(readonly) GRPCCallOptions *callOptions;
 
 /** Acquire the factory to generate a new channel with current configurations. */
 @property(readonly) id<GRPCChannelFactory> channelFactory;