Use hook_post_update_NAME instead of hook_update_N to clear the cache

Sometimes empty update hooks have been added to the upgrade path to clear the cache which can be achieved either hook_update_N or hook_post_update_NAME. Using hook_update_N can cause some issue such as:

• We shouldn't bump the schema version for no reason - there is no schema change
• This allows release managers to choose whether to backport or not without changing the patch
• It also means it any emergency patch gets released with update number(8502) then this doesn't have to change as well.

So it is recommended to use hook_post_update_NAME instead.