st/texture-cache: Don't use content size request mode for surface icons

While most GIcons passed to this function cause a StImageContent to be
created with the requested size, cairo surface based icons already are
passed as StImageContent with a preferred size corresponding to the
size of the surface they were created from. As a result icons of window
backed applications were never scaled up like the other icons. Fix this
by ignoring the content size for these case.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1751>

src/st/st-texture-cache.c

@@ -983,7 +983,6 @@ st_texture_cache_load_gicon (StTextureCache    *cache,
   if (ST_IS_IMAGE_CONTENT (icon))
     {
       return g_object_new (CLUTTER_TYPE_ACTOR,
-                           "request-mode", CLUTTER_REQUEST_CONTENT_SIZE,
                            "width", actor_size,
                            "height", actor_size,
                            "content", CLUTTER_CONTENT (icon),