Bump flask from 1.1.2 to 2.3.2 in /tests/test_gcloud/testbench (#1796)

Bumps [flask](https://github.com/pallets/flask) from 1.1.2 to 2.3.2.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@1.1.2...2.3.2)

---
updated-dependencies:
- dependency-name: flask
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

tests/test_gcloud/testbench/requirements.txt

@@ -1,5 +1,5 @@
 crc32c==2.1
-flask==1.1.2
+flask==2.3.2
 greenlet==0.4.17
 gevent==20.9.0
 gunicorn==20.0.4