Remove invite only padlocks feature flag

Fixes https://github.com/vector-im/riot-web/issues/13366

Only known issue on this is https://github.com/vector-im/riot-web/issues/12148

This has been pre-approved by Product.

src/settings/Settings.js

@@ -158,12 +158,6 @@ export const SETTINGS = {
         displayName: _td("Show info about bridges in room settings"),
         default: false,
     },
-    "feature_invite_only_padlocks": {
-        isFeature: true,
-        supportedLevels: LEVELS_FEATURE,
-        displayName: _td("Show padlocks on invite only rooms"),
-        default: true,
-    },
     "MessageComposerInput.suggestEmoji": {
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,
         displayName: _td('Enable Emoji suggestions while typing'),