Validator originally checked for <series>-{eol,eom,em,last} tags.
Since we are using branch IDs since Antelope, the validator has to
accept for example 2023.1-eom, 2023.1-eol and 2023.1-last tags instead
of antelope-<..> tags.
Change-Id: I584c34a533db25a29206606d81d95ad2daa7779c