chore(docs): bump idna from 3.10 to 3.15 in /.github/workflows/mkdocs

Bumps [idna](https://github.com/kjd/idna) from 3.10 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v3.10...v3.15)

---
updated-dependencies:
- dependency-name: idna
  dependency-version: '3.15'
  dependency-type: indirect
...

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

Author: dependabot[bot]

.github/workflows/mkdocs/requirements.txt

@@ -127,9 +127,9 @@ ghp-import==2.1.0 \
     --hash=sha256:8337dd7b50877f163d4c0289bc1f1c7f127550241988d568c1db512c4324a619 \
     --hash=sha256:9c535c4c61193c2df8871222567d7fd7e5014d835f97dc7b7439069e2413d343
     # via mkdocs
-idna==3.10 \
-    --hash=sha256:12f65c9b470abda6dc35cf8e63cc574b1c52b11df2c86030af0ac09b01b13ea9 \
-    --hash=sha256:946d195a0d259cbba61165e88e65941f16e9b36ea6ddb97f00452bae8b1287d3
+idna==3.15 \
+    --hash=sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8 \
+    --hash=sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc
     # via requests
 jinja2==3.1.6 \
     --hash=sha256:0137fb05990d35f1275a587e9aee6d56da821fc83491a0fb838183be43f66d6d \