Remove status context construction in the React side (#3331)

because it may causes flicker on the conversation when it contains blocked/muted user's status.

We use `/api/v1/statuses/{id}/context` to obtain status ids in the
conversation which filters blocked/muted user, but also uses internal
cache constructed from `in_reply_to_id` by `normalizeStatus()` in
`reducers/timelines.js` on each status loading which doesn't filter.

So statuses appears in conversation if those are cached, even those
statuses are from blocked/muted user. Then context cache will be updated
with the result of the context API and those statuses will be removed.

I have left the `normalizeStatus()` function itself which is called many
functions in the file as a placeholder for now, but maybe it should be
removed completely.