url: The function is "SDL_Unsupported" not "SDL_Unimplemented"

src/misc/dummy/SDL_sysurl.c

@@ -25,7 +25,7 @@
 int
 SDL_SYS_OpenURL(const char *url)
 {
-    return SDL_Unimplemented();
+    return SDL_Unsupported();
 }
 
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