Add missing onRestoreInstanceState override on ComposeActivity

issue: https://gitlab.e.foundation/e/backlog/-/issues/5352

In commit 73a0137d, to resolve merge
conflict, `onRestoreInstanceState` code commented out, which was
introduced in 8e4ff3ec commit by
upstream maintainer. As it can introduce bug which is not present in
upstream & as we don't modified anything which this code do, we need to
revert back to upstream change.