Update history view copy to reflect event ID-only tracking

- Rename "Clear local cache" button to "Clear local history"
- Update info text to remove references to hydrating from session/caches
- Simplify copy to remove "encrypted" references in favor of "syncing" or "history"
- Update success/error messages to match new terminology

views/history.html

@@ -16,7 +16,7 @@
           data-history-action="clear-cache"
           class="btn-ghost"
         >
-          Clear local cache
+          Clear local history
         </button>
         <button
           type="button"
@@ -58,7 +58,7 @@
 
     <div id="watchHistoryInfo" class="card p-md text-sm">
       Watch history keeps a lean list of event IDs. Details load on demand
-      from relays or your session when you open this page.
+      from relays when you open this page.
     </div>
 
     <div