clarify /jumptodate argument (#8323)

* Update SlashCommands.tsx

* remove date format from description

* update strings

src/SlashCommands.tsx

@@ -321,8 +321,8 @@ export const Commands = [
     }),
     new Command({
         command: 'jumptodate',
-        args: '<date>',
-        description: _td('Jump to the given date in the timeline (YYYY-MM-DD)'),
+        args: '<YYYY-MM-DD>',
+        description: _td('Jump to the given date in the timeline'),
         isEnabled: () => SettingsStore.getValue("feature_jump_to_date"),
         runFn: function(roomId, args) {
             if (args) {