Fix docker hub tag in link for releases

[LelouBil]

What this PR does / why we need it:

In the releases body, the link to the docker tags is broken because docker tags don't have a "v" prefix like the tags on github

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Test it if you want to merge now, I don't have the time to test it now and will do so in the couple next days if you want.

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• [x] the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[jonasvoelcker]

Hi @LelouBil,

we had some problem with one of our plugins and had to release multiple times. Now we know that this change works fine, thanks a lot!