chore: update requirements.txt to address dependabot security alerts. (#1936)

Created by running:
pip-compile requirements.in --generate-hashes --upgrade within synthtool/gcp/templates/java_library/.kokoro and synthtool/docker/owlbot/java/src/
Source-Link: googleapis/synthtool@853dbcd
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-java:latest@sha256:084ad4c60551b075846bcb2405ec1c14b0d00ec1eb5503d4dd0d2a92cdc2d3e2

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-java:latest
-  digest: sha256:a6aa751984f1e905c3ae5a3aac78fc7b68210626ce91487dc7ff4f0a06f010cc
-# created: 2024-01-22T14:14:20.913785597Z
+  digest: sha256:084ad4c60551b075846bcb2405ec1c14b0d00ec1eb5503d4dd0d2a92cdc2d3e2
+# created: 2024-03-15T14:33:32.257974519Z