Fixed #7564

Summary:
Fix for some firewall with ModSecurity
 rules for MULTIPART_STRICT_ERROR, namely MULTIPART_BOUNDARY_QUOTED.
Closes #10876

Reviewed By: javache

Differential Revision: D4176229

Pulled By: ericvicenti

fbshipit-source-id: 8db819bd3e9b23fa3c1802c48091bb4c44358381

Libraries/Network/RCTNetworking.mm

@@ -116,7 +116,7 @@ - (RCTURLRequestCancellationBlock)handleResult:(NSDictionary<NSString *, id> *)r
   // We've processed the last item. Finish and return.
   [_multipartBody appendData:[[NSString stringWithFormat:@"--%@--\r\n", _boundary]
                               dataUsingEncoding:NSUTF8StringEncoding]];
-  NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=\"%@\"", _boundary];
+  NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", _boundary];
   return _callback(nil, @{@"body": _multipartBody, @"contentType": contentType});
 }