Bug#1106574: release-notes FTBFS with gbp buildpackage

> > Is there a file "debian/compat"?
> >
> > This file is obsolete. Please use debhelper-compat (=13) in debian/control.

Found some other issues --
- most of debian/rules can replaced with a simple call to dh
- missing build-dep on git (Makefile uses it to set the last-modified date)
- the build of pdf does not work for el, zh_CN or zh_TN -- they should
be in LANGS_NOPDF in Makefile
   (all the other languages in LANGS_NOPDF also still failed for me -
it may be that
     adding a dep on texlive-xelatex and some font packages might
help, possibly.)
-  the .gitlab-ci.yml tries to use a build-profile to disable pdf,
but there's no implementation of this in debian/control or
debian/rules: every CI job is currently installing
texlive ecosystem, despite only building the html format

a MR to fix all that is here:
https://salsa.debian.org/ddp-team/release-notes/-/merge_requests/247

i can then run  "gbp buildpackage --profiles=pkg.release-notes.nopdf"
and it works without needing to install texlive in the chroot
(given sbuild puts the chroot in tmpfs you would need a lot of memory
to build all the pdfs).

After the build i can dpkg-extract the .deb and view the html without
having to clutter the host system at all.