build(deps): bump certifi from 2022.6.15 to 2023.7.22 in /.kokoro

Bumps [certifi](https://github.com/certifi/python-certifi) from 2022.6.15 to 2023.7.22.
- [Commits](certifi/python-certifi@2022.06.15...2023.07.22)

---
updated-dependencies:
- dependency-name: certifi
  dependency-type: indirect
...

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

.kokoro/requirements.txt

@@ -34,9 +34,9 @@ cachetools==5.2.0 \
     --hash=sha256:6a94c6402995a99c3970cc7e4884bb60b4a8639938157eeed436098bf9831757 \
     --hash=sha256:f9f17d2aec496a9aa6b76f53e3b614c965223c061982d434d160f930c698a9db
     # via google-auth
-certifi==2022.6.15 \
-    --hash=sha256:84c85a9078b11105f04f3036a9482ae10e4621616db313fe045dd24743a0820d \
-    --hash=sha256:fe86415d55e84719d75f8b69414f6438ac3547d2078ab91b67e779ef69378412
+certifi==2023.7.22 \
+    --hash=sha256:539cc1d13202e33ca466e88b2807e29f4c13049d6d87031a3c110744495cb082 \
+    --hash=sha256:92d6037539857d8206b8f6ae472e8b77db8058fec5937a1ef3f54304089edbb9
     # via requests
 cffi==1.15.1 \
     --hash=sha256:00a9ed42e88df81ffae7a8ab6d9356b371399b91dbdf0c3cb1e84c03a13aceb5 \