Clean up removed permissions (#6035)

- indices:admin/aliases/exists
- indices:admin/shrink
- indices:admin/synced_flush
- indices:admin/types/exists

Signed-off-by: Taeik Lim <sibera21@gmail.com>

_security/access-control/permissions.md

@@ -381,7 +381,6 @@ See [Index templates]({{site.url}}{{site.baseurl}}/im-plugin/index-templates/).
 These permissions apply to an index or index pattern. You might want a user to have read access to all indexes (that is, `*`), but write access to only a few (for example, `web-logs` and `product-catalog`).
 
 - indices:admin/aliases
-- indices:admin/aliases/exists
 - indices:admin/aliases/get
 - indices:admin/analyze
 - indices:admin/cache/clear
@@ -416,12 +415,9 @@ These permissions apply to an index or index pattern. You might want a user to h
 - indices:admin/seq_no/global_checkpoint_sync
 - indices:admin/settings/update
 - indices:admin/shards/search_shards
-- indices:admin/shrink
-- indices:admin/synced_flush
 - indices:admin/template/delete
 - indices:admin/template/get
 - indices:admin/template/put
-- indices:admin/types/exists
 - indices:admin/upgrade
 - indices:admin/validate/query
 - indices:data/read/explain