chore(deps): update dependency pem to v23 (GoogleCloudPlatform#10276)

* chore(deps): update dependency pem to v23

* Update requirements.txt

---------

Co-authored-by: Karl Weinmeister <[email protected]>

Author: renovate-bot

kms/attestations/requirements.txt

@@ -1,3 +1,4 @@
 cryptography==41.0.1
-pem==21.2.0
-requests==2.31.0
+pem==21.2.0; python_version < '3.8'
+pem==23.1.0; python_version > '3.7'
+requests==2.31.0