chore(deps): bump filelock from 3.14.0 to 3.20.3 in /.kokoro/docker/docs

Bumps [filelock](https://github.com/tox-dev/py-filelock) from 3.14.0 to 3.20.3.
- [Release notes](https://github.com/tox-dev/py-filelock/releases)
- [Changelog](https://github.com/tox-dev/filelock/blob/main/docs/changelog.rst)
- [Commits](tox-dev/filelock@3.14.0...3.20.3)

---
updated-dependencies:
- dependency-name: filelock
  dependency-version: 3.20.3
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.kokoro/docker/docs/requirements.txt

@@ -16,9 +16,9 @@ distlib==0.3.8 \
     --hash=sha256:034db59a0b96f8ca18035f36290806a9a6e6bd9d1ff91e45a7f172eb17e51784 \
     --hash=sha256:1530ea13e350031b6312d8580ddb6b27a104275a31106523b8f123787f494f64
     # via virtualenv
-filelock==3.14.0 \
-    --hash=sha256:43339835842f110ca7ae60f1e1c160714c5a6afd15a2873419ab185334975c0f \
-    --hash=sha256:6ea72da3be9b8c82afd3edcf99f2fffbb5076335a5ae4d03248bb5b6c3eae78a
+filelock==3.20.3 \
+    --hash=sha256:18c57ee915c7ec61cff0ecf7f0f869936c7c30191bb0cf406f1341778d0834e1 \
+    --hash=sha256:4b0dda527ee31078689fc205ec4f1c1bf7d56cf88b6dc9426c4f230e46c2dce1
     # via virtualenv
 nox==2024.4.15 \
     --hash=sha256:6492236efa15a460ecb98e7b67562a28b70da006ab0be164e8821177577c0565 \