Use the path filter when triggering contracts-docs-publish-preview

Instead of running the `contracts-docs-publish-preview` job on update of every
PR, we want to run it only when PR modifies contracts or the workflow itself.

.github/workflows/contracts-docs.yml

@@ -36,7 +36,7 @@ jobs:
  name: Publish preview of contracts documentation
  needs: docs-detect-changes
  if: |
- github.event_name == 'pull_request'
+ needs.docs-detect-changes.outputs.path-filter == 'true'
  || github.event_name == 'push'
  || github.event_name == 'workflow_dispatch'
  uses: keep-network/ci/.github/workflows/reusable-solidity-docs.yml@main