ci: don't fail job on failed personal Telegram notification

To be honest, I have not proceeded with necessary actions to receive
personal Telegram notifications for my branches, because GitHub already
sends them to my email.

I kept this feature (I don't know, whether someone uses it), but let the
action ignore failures in the case.

A failed attempt to send the notification from `master`, a release
branch (`1.10`, `2.8`, ...) or a tag will fail the job as before. The
change affects only personal notifications for developer branches.

Fixes https://github.com/tarantool/tarantool-qa/issues/130