deprecate: on-disk encryption

Why?
1. there're still a lot issues on it and there's no resource to
maintain and develop it considering we need to support it on all the
platforms.
2. it creates more bugs with Logseq Sync.

src/main/frontend/state.cljs

@@ -648,10 +648,6 @@ Similar to re-frame subscriptions"
   []
   (:editor/logical-outdenting? (sub-config)))
 
-(defn enable-encryption?
-  [repo]
-  (:feature/enable-encryption? (sub-config repo)))
-
 (defn doc-mode-enter-for-new-line?
   []
   (and (document-mode?)