[DRE-maint] Bug#967999: version 6.x has support for rails 6

[Cédric Boutillier]

The last upstream version 6.3.0 has support for Rails 6.

I have imported the package in the Ruby team salsa group (it was missing
for some reason), at the place expected from the Vcs fields.
I upgraded roughly the package, and noticed (only?)
two test failures (and no error), that I could not fix yet.

Cheers

Cédric