build(deps): bump slack-sdk in /.github/actions/pr_notifier

Bumps [slack-sdk](https://github.com/slackapi/python-slack-sdk) from 3.21.3 to 3.33.0.
- [Release notes](https://github.com/slackapi/python-slack-sdk/releases)
- [Commits](slackapi/python-slack-sdk@v3.21.3...v3.33.0)

---
updated-dependencies:
- dependency-name: slack-sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/actions/pr_notifier/requirements.txt

@@ -207,9 +207,9 @@ six==1.16.0 \
     --hash=sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926 \
     --hash=sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254
     # via pynacl
-slack-sdk==3.21.3 \
-    --hash=sha256:20829bdc1a423ec93dac903470975ebf3bc76fd3fd91a4dadc0eeffc940ecb0c \
-    --hash=sha256:de3c07b92479940b61cd68c566f49fbc9974c8f38f661d26244078f3903bb9cc
+slack-sdk==3.33.0 \
+    --hash=sha256:070eb1fb355c149a5f80fa0be6eeb5f5588e4ddff4dd76acf060454435cb037e \
+    --hash=sha256:853bb55154115d080cae342c4099f2ccb559a78ae8d0f5109b49842401a920fa
     # via -r requirements.in
 urllib3==1.26.6 \
     --hash=sha256:39fb8672126159acb139a7718dd10806104dec1e2f0f6c88aab05d17df10c8d4 \