Delete obsolete tau trigger packages (!22625) · Merge requests · atlas / athena

Deleting the packages:

Trigger/TrigAlgorithms/TrigT2IDTau
Trigger/TrigAlgorithms/TrigT2Tau
Trigger/TrigAlgorithms/TrigTauDiscriminant

They have been irrelevant already for 2018 data taking and now all remaining dependencies have been removed in master thanks to @martindl.

Jira tracking deleted trigger packages: ATR-19150

Delete obsolete tau trigger packages