Remove dead code in gr-storage

Change-Id: Id1e024c21f9f41d67654cbbcabc4af0595a105e0
diff --git a/polygerrit-ui/app/elements/shared/gr-storage/gr-storage.js b/polygerrit-ui/app/elements/shared/gr-storage/gr-storage.js
index 6146e0f..0690950 100644
--- a/polygerrit-ui/app/elements/shared/gr-storage/gr-storage.js
+++ b/polygerrit-ui/app/elements/shared/gr-storage/gr-storage.js
@@ -76,14 +76,6 @@
       this._storage.removeItem(this._getEditableContentKey(key));
     },
 
-    getPreferences() {
-      return this._getObject('localPrefs');
-    },
-
-    savePreferences(localPrefs) {
-      this._setObject('localPrefs', localPrefs || null);
-    },
-
     _getDraftKey(location) {
       const range = location.range ?
           `${location.range.start_line}-${location.range.start_character}` +