Bump urllib3 from 2.6.0 to 2.6.3 in /docs

Bumps [urllib3](https://github.com/urllib3/urllib3) from 2.6.0 to 2.6.3.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@2.6.0...2.6.3)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-version: 2.6.3
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -1808,9 +1808,9 @@ uncertainties==3.2.2 \
     # via
     #   -r requirements/dev-requirements.txt
     #   lmfit
-urllib3==2.6.0 \
-    --hash=sha256:c90f7a39f716c572c4e3e58509581ebd83f9b59cced005b7db7ad2d22b0db99f \
-    --hash=sha256:cb9bcef5a4b345d5da5d145dc3e30834f58e8018828cbc724d30b4cb7d4d49f1
+urllib3==2.6.3 \
+    --hash=sha256:1b62b6884944a57dbe321509ab94fd4d3b307075e0c2eae991ac71ee15ad38ed \
+    --hash=sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4
     # via requests
 uv==0.9.6 \
     --hash=sha256:0169a85d3ba5ef1c37089d64ff26de573439ca84ecf549276a2eee42d7f833f2 \