dependabot: Keep sass at < 1.80

sass 1.80 (and 2.x) introduces tons of "@import rules are deprecated".
These are unfixable on our side due to PatternFly using them
extensively.

We don't need any new sass features, so stick to 1.79.x. Explicitly not
ignore 3.x (which will drop @import) to get a reminder in the future to
try and clean this up again.

Same as https://github.com/cockpit-project/cockpit/pull/21155

Closes #1017

.github/dependabot.yml

@@ -29,6 +29,11 @@ updates:
           - "@types*"
           - "types*"
 
+    ignore:
+      # https://github.com/cockpit-project/cockpit/issues/21151
+      - dependency-name: "sass"
+        versions: ["1.80.x", "2.x"]
+
   - package-ecosystem: "github-actions"
     directory: "/"
     open-pull-requests-limit: 3