Fix FPS menu in "Format" panel not following translation setting

The FPS menu was using a cached value which wasn't being refreshed
when translation changed.

Add `bpy.app.handlers.translation_update_post` handler which runs
when translation changes, this can be used to clear any cached UI
values.

Ref !117049

source/blender/blenkernel/BKE_callbacks.h

@@ -109,6 +109,7 @@ typedef enum {
   BKE_CB_EVT_COMPOSITE_CANCEL,
   BKE_CB_EVT_ANIMATION_PLAYBACK_PRE,
   BKE_CB_EVT_ANIMATION_PLAYBACK_POST,
+  BKE_CB_EVT_TRANSLATION_UPDATE_POST,
   BKE_CB_EVT_EXTENSION_REPOS_UPDATE_PRE,
   BKE_CB_EVT_EXTENSION_REPOS_UPDATE_POST,
   BKE_CB_EVT_TOT,