Bug#909703: python3-gi: Should not depend on python3-cairo

[Jeremy Bicha]

Package: python3-gi
Version: 3.30.1-1
Severity: important

An Ubuntu developer pointed out that python3-gi has recently gained a
dependency on python3-cairo. This is unexpected because there is a
separate python3-gi-cairo package produced by the same source package.
It also significantly increases python3-gi's dependency chain.

I cannot duplicate this bug if I revert
https://salsa.debian.org/gnome-team/pygobject/commit/b5116ffb (the
switch to pybuild)

Thanks,
Jeremy Bicha