chore(python): update dependencies in .kokoro/requirements.txt (#1180)

Source-Link: googleapis/synthtool@e3a1277
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:452901c74a22f9b9a3bd02bce780b8e8805c97270d424684bff809ce5be8c2a2

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <[email protected]>

Author: gcf-owl-bot[bot]

packages/google-auth/.github/.OwlBot.lock.yaml

@@ -13,4 +13,4 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:993a058718e84a82fda04c3177e58f0a43281a996c7c395e0a56ccc4d6d210d7
+  digest: sha256:452901c74a22f9b9a3bd02bce780b8e8805c97270d424684bff809ce5be8c2a2