fix(cache-cleanup): replace newline with space in cache-keys output (…

…#536)

.github/workflows/cache-cleanup.yaml

@@ -36,7 +36,7 @@ jobs:
             # Get cache keys that don't include the branch's SHA (if not a PR)
             gh actions-cache list -R ${{ github.repository }} -B $BRANCH -L 100 --key $KEY --order asc --sort last-used | cut -f 1 > cache-keys.txt
             [ -z "${{ github.event.pull_request }}" ] && grep -v ${{ github.sha }} cache-keys.txt > cache-keys.txt.tmp && mv cache-keys.txt.tmp cache-keys.txt
-            echo cache-keys="$(cat cache-keys.txt)" >> $GITHUB_OUTPUT
+            echo cache-keys="$(cat cache-keys.txt | tr '\n' '[:space:]')" >> $GITHUB_OUTPUT
           fi
 
       - env: