Apparent requirement of `debian/watch` without alternatives is misleading

[CarlosNihelton]

Hi folks! Thanks for improving this documentation set.

I'm working through an MIR of a package which does not have a debian/watch file, but instead it relies on debian/upstream/metadata, which git-buildpackage reads and learns from it on how to fetch new upstream releases, completely replacing uscan and the need for debian/watch (see DEP-12 for more information). Yet, the MIR template implies that debian/watch is the only automation available and offers as fallback a README.source with manual steps for the simple-enough cases.

Here's the snippet in the mir-reporters-template that I'm talking about:
https://github.com/ubuntu/ubuntu-project-docs/blob/main/docs/MIR/mir-reporters-template.md?plain=1#L271-L278

We should acknowledge that for packages maintained with git-buildpackage a debian/upstream/metadata is expected, and debian/watch as a fallback.