Change constness

src/core/lib/iomgr/error.c

@@ -510,14 +510,14 @@ grpc_error *grpc_os_error(const char *file, int line, int err,
 #ifdef GPR_WINDOWS
 grpc_error *grpc_wsa_error(const char *file, int line, int err,
                            const char *call_name) {
-  char *utf8_message = gpr_format_message(err);
+  const char *utf8_message = gpr_format_message(err);
   grpc_error *error = grpc_error_set_str(
       grpc_error_set_str(
           grpc_error_set_int(grpc_error_create(file, line, "OS Error", NULL, 0),
                              GRPC_ERROR_INT_WSA_ERROR, err),
           GRPC_ERROR_STR_OS_ERROR, utf8_message),
       GRPC_ERROR_STR_SYSCALL, call_name);
-  gpr_free(utf8_message);
+  gpr_free((void *)utf8_message);
   return error;
 }
 #endif