Remove mermaid from github actions, breaking build

Author: tonykay

.github/workflows/gh-pages.yml

@@ -35,7 +35,7 @@ jobs:
         with:
           node-version: '20'
       - name: install antora
-        run: npm i -g @antora/cli@3.1 @antora/site-generator@3.1 @sntke/antora-mermaid-extension@0.0.9
+        run: npm i -g @antora/cli@3.1 @antora/site-generator@3.1
       - name: antora generate
         run: antora --fetch site.yml
       - name: upload pages artifact