fix(lychee): exclude www.gnu.org (often down)

templates/validation.yml

@@ -68,7 +68,7 @@ check-links:
     entrypoint: [""]
   stage: build
   script:
-    - lychee --exclude-path CHANGELOG.md --exclude-path SECURITY.md $LYCHEE_EXTRA_OPTS *.md
+    - lychee --exclude www.gnu.org --exclude-path CHANGELOG.md --exclude-path SECURITY.md $LYCHEE_EXTRA_OPTS *.md
 
 tbc-check:
   image: