Cleanup: added 'Versioning code until next subversion bump goes here'

The `do_versions_after_linking_280()` function was missing a placeholder
for the newly added versioning code. I copied the comments from the
`blo_do_versions_280()` function.

No functional changes.

source/blender/blenloader/intern/versioning_280.c

@@ -1537,7 +1537,18 @@ void do_versions_after_linking_280(Main *bmain, ReportList *UNUSED(reports))
     }
   }
 
+  /**
+   * Versioning code until next subversion bump goes here.
+   *
+   * \note Be sure to check when bumping the version:
+   * - "versioning_userdef.c", #BLO_version_defaults_userpref_blend
+   * - "versioning_userdef.c", #do_versions_theme
+   *
+   * \note Keep this message at the bottom of the function.
+   */
   {
+    /* Keep this block, even when empty. */
+
     /* During development of Blender 2.80 the "Object.hide" property was
      * removed, and reintroduced in 5e968a996a53 as "Object.hide_viewport". */
     LISTBASE_FOREACH (Object *, ob, &bmain->objects) {