Cannot build gtk3.spec in src rpm due to missing avahi-gobject

Description of problem:

Trying to build gtk3-3.24.31-2.el9.src.rpm fails due to gtk3.spec file referencing "BuildRequires: pkgconfig(avahi-gobject)" - no such file exist in Centos9-Stream repos.

Version-Release number of selected component (if applicable):

3.24.31-2.el9

How reproducible:

Every time. All installs.

Steps to Reproduce:
1. Download gtk3-3.24.31-2.el9.src.rpm
2. Try to rebuild with mock / rpmbuild
3. Fails with package / library "avahi-gobject" not found

Actual results:

Should build

Expected results:

Additional info: