Bug 1969769 - Change uses of ast.Str with ast.Constant. r=firefox-build-system-review...

Bug 1969769 - Change uses of ast.Str with ast.Constant. r=firefox-build-system-reviewers,ahochheiden

ast.Str was deprecated in python 3.12 and removed in 3.14. It inherited
from ast.Constant, `Str.s` was equivalent to `Constant.value`, so we can
use the latter on both old and newer python versions.

Differential Revision: https://phabricator.services.mozilla.com/D261512

Gbp-Pq: Topic fixes
Gbp-Pq: Name Bug-1969769-Change-uses-of-ast.Str-with-ast.Constant.patch