package.json: Downgrade sass to 1.79

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

The dependabot change from commit 6cc062f76f will prevent updates
in the future, but it landed when package.json already had 1.80.

package.json

@@ -41,7 +41,7 @@
     "htmlparser": "1.7.7",
     "jed": "1.1.1",
     "qunit": "2.22.0",
-    "sass": "1.80.3",
+    "sass": "1.79.6",
     "stylelint": "16.10.0",
     "stylelint-config-recommended-scss": "14.0.0",
     "stylelint-config-standard": "36.0.1",