Bug#1113795: devscripts: debian-watch version 5 gitlab template does not handle version with "v" prefix well

[Jeremy Bícha]

The GitHub template correctly handles the common v prefix.
https://qa.debian.org/cgi-bin/watch?pkg=mousai

But the GitLab template does not:
https://qa.debian.org/cgi-bin/watch?pkg=apostrophe

Thanks,
Jeremy Bícha