Bump markdown from 3.7 to 3.8 in /requirements (#23312)

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.7 to 3.8.
- [Release notes](https://github.com/Python-Markdown/markdown/releases)
- [Changelog](https://github.com/Python-Markdown/markdown/blob/master/docs/changelog.md)
- [Commits](Python-Markdown/markdown@3.7...3.8)

---
updated-dependencies:
- dependency-name: markdown
  dependency-version: '3.8'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements/prod.txt

@@ -1209,9 +1209,9 @@ watchdog[watchmedo]==3.0.0 \
     --hash=sha256:c9d8c8ec7efb887333cf71e328e39cffbf771d8f8f95d308ea4125bf5f90ba64 \
     --hash=sha256:d00e6be486affb5781468457b21a6cbe848c33ef43f9ea4a73b4882e5f188a44 \
     --hash=sha256:d429c2430c93b7903914e4db9a966c7f2b068dd2ebdd2fa9b9ce094c7d459f33
-Markdown==3.7 \
-    --hash=sha256:2ae2471477cfd02dbbf038d5d9bc226d40def84b4fe2986e49b59b6b472bbed2 \
-    --hash=sha256:7eb6df5690b81a1d7942992c97fad2938e956e79df20cbc6186e9c3a77b1c803
+Markdown==3.8 \
+    --hash=sha256:794a929b79c5af141ef5ab0f2f642d0f7b1872981250230e72682346f7cc90dc \
+    --hash=sha256:7df81e63f0df5c4b24b7d156eb81e4690595239b7d70937d0409f1b0de319c6f
 pyuwsgi==2.0.28.post1 \
     --hash=sha256:06a0294910de374ff43032b41333f7f9b62d59308b7f3eea29bc64d78fb93613 \
     --hash=sha256:0b1c131288b6b473e39c5b02e63c34b64422665749dcadee41ef98d64b5db5d0 \