ci: report PRs from TarantoolBot to main chat

Report workflow failures in PRs made by TarantoolBot to the same chat
as with stable branches. Such PRs are used for automated integration
testing, so it's important for the team to notice failures in them.
There is no personal chat for TarantoolBot and no need to make one.

NO_DOC=CI reporting
NO_TEST=CI reporting
NO_CHANGELOG=CI reporting

(cherry picked from commit 8ebfa611)