ci: fix lychee-action pin to existing commit SHA (v2.9.0) (#946)

Author: devitway

.github/workflows/link-check.yml

@@ -29,7 +29,7 @@ jobs:
           restore-keys: lychee-
 
       - name: Run lychee link checker
-        uses: lycheeverse/lychee-action@f613a0156d062e3ecbf2dfa68ab1abcbcae85654 # v2.4.1
+        uses: lycheeverse/lychee-action@e7477775783ea5526144ba13e8db5eec57747ce8 # v2.9.0
         with:
           args: >-
             --cache