ci: use api-key input instead of env in writing agent

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>

Author: dvdksn

.github/workflows/agent-writer.yml

@@ -64,8 +64,8 @@ jobs:
 
             Keep the PR body brief and practical. Don't over-explain or add sections
             that aren't needed.
+          anthropic-api-key: ${{ secrets.ANTHROPIC_API_KEY }}
         env:
-          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Check for changes