Clang-Tidy fixes (#6725)

(cherry picked from commit 3c501b963d)

test/testdisplayinfo.c

@@ -80,7 +80,7 @@ int main(int argc, char *argv[])
                 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "    MODE %d: failed to query (%s)\n", m, SDL_GetError());
             } else {
                 char prefix[64];
-                SDL_snprintf(prefix, sizeof(prefix), "    MODE %d", m);
+                (void)SDL_snprintf(prefix, sizeof prefix, "    MODE %d", m);
                 print_mode(prefix, &mode);
             }
         }