Attention request button applies incorrect action when state is outdated

If attention request state has become stale then request attention button might apply an unexpected action.

Steps to reproduce:

1. Open an MR in two different tabs (1 and 2).
2. In tab 1 request attention for the reviewer.
3. Repeat this in tab 2.

Expected: request attention button in tab 2 should do nothing.

Reality: request attention button in tab 2 removes attention request.