fix: offline banned user not leaving channel upon reconnect in mobile view (#1194)

Fixes [AC-1893](https://sendbird.atlassian.net/browse/AC-1893)

### Changelogs
- Fixed a bug where offline banned user is not leaving channel upon
reconnect in mobile view

[AC-1893]:
https://sendbird.atlassian.net/browse/AC-1893?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: chohongm

src/modules/GroupChannel/context/GroupChannelProvider.tsx

@@ -193,10 +193,12 @@ export const GroupChannelProvider = (props: GroupChannelProviderProps) => {
     onChannelDeleted: () => {
       setCurrentChannel(null);
       setFetchChannelError(null);
+      onBackClick?.();
     },
     onCurrentUserBanned: () => {
       setCurrentChannel(null);
       setFetchChannelError(null);
+      onBackClick?.();
     },
     onChannelUpdated: (channel) => setCurrentChannel(channel),
     logger: logger as any,