security/py-google-auth: Update to 2.21.0

Changes:	https://github.com/googleapis/google-auth-library-python/releases

security/py-google-auth/Makefile

 PORTNAME=	google-auth
-PORTVERSION=	2.19.1
+PORTVERSION=	2.21.0
 CATEGORIES=	security python
 MASTER_SITES=	PYPI
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}

security/py-google-auth/distinfo

-TIMESTAMP = 1685792334
-SHA256 (google-auth-2.19.1.tar.gz) = a9cfa88b3e16196845e64a3658eb953992129d13ac7337b064c6546f77c17183
-SIZE (google-auth-2.19.1.tar.gz) = 230290
+TIMESTAMP = 1688166314
+SHA256 (google-auth-2.21.0.tar.gz) = b28e8048e57727e7cf0e5bd8e7276b212aef476654a09511354aa82753b45c66
+SIZE (google-auth-2.21.0.tar.gz) = 230720