chore(deps): bump pyjwt to from 2.8.0 to 2.12.0. (#329)

PyJWT is only used in tests, so the vulnerability (CVE-2026-32597) is
not that consequential, but worth updating anyway.

Author: jasiekmarc

callouts/python/requirements-test.txt

@@ -1,3 +1,3 @@
 pytest==7.4.2
 google-cloud-logging==3.9.0
-pyjwt[crypto]==2.8.0
+pyjwt[crypto]==2.12.0