[ Reason ]
Version 4.7.3 of the Debian policy recommends that the 'Priority'
field is removed if it has the default value ("optional"). This
change was applied to webkit2gtk 2.50.5-1 but it was not reverted
when preparing the bookworm backport.

[ Impact ]
reprepro is broken because of this missing field, see #1140609

[ Tests ]
N/A

[ Risks ]
This is a trivial change

[ Checklist ]
  [x] *all* changes are documented in the d/changelog
  [x] I reviewed all changes and I approve them
  [x] attach debdiff against the package in (old)stable
  [x] the issue is verified as fixed in unstable

Berto