cogl: Remove cogl_offscreen_new_to_texture()

It's no longer used, and has been deprecated for a long time.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1496

cogl/cogl/cogl-framebuffer.c

@@ -829,23 +829,6 @@ _cogl_offscreen_new_with_texture_full (CoglTexture *texture,
   return ret;
 }
 
-/* XXX: deprecated api */
-CoglOffscreen *
-cogl_offscreen_new_to_texture (CoglTexture *texture)
-{
-  CoglOffscreen *ret = _cogl_offscreen_new_with_texture_full (texture, 0, 0);
-  GError *error = NULL;
-
-  if (!cogl_framebuffer_allocate (COGL_FRAMEBUFFER (ret), &error))
-    {
-      cogl_object_unref (ret);
-      g_error_free (error);
-      ret = NULL;
-    }
-
-  return ret;
-}
-
 CoglOffscreen *
 cogl_offscreen_new_with_texture (CoglTexture *texture)
 {

cogl/cogl/cogl-offscreen.h

@@ -99,30 +99,6 @@ GType cogl_offscreen_get_gtype (void);
 COGL_EXPORT CoglOffscreen *
 cogl_offscreen_new_with_texture (CoglTexture *texture);
 
-/**
- * cogl_offscreen_new_to_texture:
- * @texture: A #CoglTexture pointer
- *
- * This creates an offscreen buffer object using the given @texture as the
- * primary color buffer. It doesn't just initialize the contents of the
- * offscreen buffer with the @texture; they are tightly bound so that
- * drawing to the offscreen buffer effectivly updates the contents of the
- * given texture. You don't need to destroy the offscreen buffer before
- * you can use the @texture again.
- *
- * <note>This only works with low-level #CoglTexture types such as
- * #CoglTexture2D and not with meta-texture types such as
- * #CoglTexture2DSliced.</note>
- *
- * Return value: (transfer full): a newly instantiated #CoglOffscreen
- *   framebuffer or %NULL if it wasn't possible to create the
- *   buffer.
- * Deprecated: 1.16: Use cogl_offscreen_new_with_texture instead.
- */
-COGL_DEPRECATED_FOR (cogl_offscreen_new_with_texture)
-COGL_EXPORT CoglOffscreen *
-cogl_offscreen_new_to_texture (CoglTexture *texture);
-
 /**
  * cogl_is_offscreen:
  * @object: A pointer to a #CoglObject