Remove constraints unnecessary since bullseye (oldstable)

Remove constraints unnecessary since bullseye (oldstable)

* Build-Depends: Drop versioned constraint on gobject-introspection (>= 1.51.5).
* Build-Depends: Drop versioned constraint on libavahi-client-dev (>= 0.6.31).
* Build-Depends: Drop versioned constraint on libavahi-glib-dev (>= 0.6.31).
* Build-Depends: Drop versioned constraint on libgirepository1.0-dev (>= 1.51.5).
* Build-Depends: Drop versioned constraint on libglib2.0-dev (>= 2.66.0).
* Build-Depends: Drop versioned constraint on libmount-dev (>= 2.23).
* libostree-1-1: Drop conflict with removed package flatpak (<< 0.8.7-2~) in Breaks.
* libostree-dev: Drop versioned constraint on libglib2.0-dev (>= 2.66.0) in Depends.
* Remove 2 maintscript entries from 1 files.

Changes-By: deb-scrub-obsolete