security(docs): bump mkdocs-material to 9.8.0 (CVE-2026-73295)

Bumps mkdocs-material 9.7.6 -> 9.8.0 (latest), which resolves Dependabot
alert #1. mkdocs-material 7.2.0 through 9.7.6 contains a DOM-based XSS in
the optional `search.suggest` feature via a crafted `q` URL parameter
(GHSA-xvg9-69gf-fjrf, CVE-2026-73295, CVSS 5.4); fixed in 9.7.7 and later.

Documentation-site build dependency only (website/requirements.txt, used by
.github/workflows/docs.yml); does not affect WELA itself.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

website/requirements.txt

@@ -2,6 +2,6 @@
 # Used by .github/workflows/docs.yml and for local previews:
 #   pip install -r website/requirements.txt
 #   mkdocs serve -f website/mkdocs.yml
-mkdocs-material==9.7.6
+mkdocs-material==9.8.0
 mkdocs-glightbox==0.5.2
 mkdocs-static-i18n==1.3.1