Update spring-doc-actions to v0.0.21

This updates the version to the spring-doc-actions in order to purge the
CloudFlare Cache using a prefix rather than a set of URLs.

Signed-off-by: onobc <[email protected]>
(cherry picked from commit 29079e1)

Author: onobc

.github/workflows/ci.yml

@@ -205,15 +205,15 @@ jobs:
         run: |
           ./gradlew antora
       - name: Publish Docs
-        uses: spring-io/spring-doc-actions/[email protected].20
+        uses: spring-io/spring-doc-actions/[email protected].21
         with:
           docs-username: ${{ secrets.DOCS_USERNAME }}
           docs-host: ${{ secrets.DOCS_HOST }}
           docs-ssh-key: ${{ secrets.DOCS_SSH_KEY }}
           docs-ssh-host-key: ${{ secrets.DOCS_SSH_HOST_KEY }}
           site-path: spring-pulsar-docs/build/site
       - name: Bust Clouflare Cache
-        uses: spring-io/spring-doc-actions/[email protected].20
+        uses: spring-io/spring-doc-actions/[email protected].21
         with:
           context-root: spring-pulsar
           cloudflare-zone-id: ${{ secrets.CLOUDFLARE_ZONE_ID }}