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

Bumps [slack-sdk](https://github.com/slackapi/python-slack-sdk) from 3.13.0 to 3.19.3.
- [Release notes](https://github.com/slackapi/python-slack-sdk/releases)
- [Changelog](https://github.com/slackapi/python-slack-sdk/blob/main/docs-v2/changelog.html)
- [Commits](slackapi/python-slack-sdk@v3.13.0...v3.19.3)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/actions/pr_notifier/requirements.txt

@@ -111,9 +111,9 @@ six==1.16.0 \
     --hash=sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926 \
     --hash=sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254
     # via pynacl
-slack_sdk==3.13.0 \
-    --hash=sha256:54f2a5f7419f1ab932af9e3200f7f2f93db96e0f0eb8ad7d3b4214aa9f124641 \
-    --hash=sha256:aae6ce057e286a5e7fe7a9f256e85b886eee556def8e04b82b08f699e64d7f67
+slack-sdk==3.19.3 \
+    --hash=sha256:316574ffaf0f5c55bd08476b0a34f3bd2caa9b90b814859bc22922f25934d3aa \
+    --hash=sha256:88ddf46f42f95568cffbab8c69de7e7bfacce9b13829d9214a8aee2b70b0a4b7
     # via -r requirements.in
 urllib3==1.26.6 \
     --hash=sha256:39fb8672126159acb139a7718dd10806104dec1e2f0f6c88aab05d17df10c8d4 \