chore(deps): update dependency google-auth to v2.39.0 (googleapis#645)

Author: renovate-bot

requirements.txt

@@ -134,9 +134,9 @@ google-api-core[grpc]==2.24.2 \
     # via
     #   google-cloud-core
     #   google-cloud-spanner
-google-auth==2.38.0 \
-    --hash=sha256:8285113607d3b80a3f1543b75962447ba8a09fe85783432a784fdeef6ac094c4 \
-    --hash=sha256:e7dae6694313f434a2727bf2906f27ad259bae090d7aa896590d86feec3d9d4a
+google-auth==2.39.0 \
+    --hash=sha256:0150b6711e97fb9f52fe599f55648950cc4540015565d8fbb31be2ad6e1548a2 \
+    --hash=sha256:73222d43cdc35a3aeacbfdcaf73142a97839f10de930550d89ebfe1d0a00cde7
     # via
     #   google-api-core
     #   google-cloud-core