Update run-markdownsnippets to run only on workflow_dispatch

Author: mauroservienti

.github/workflows/run-markdownsnippets.yml

@@ -1,10 +1,6 @@
 name: MarkdownSnippets
 on:
-  push:
-    branches:
-      - '**'
-    tags-ignore:
-      - '*.*'
+  workflow_dispatch:
 jobs:
   documentation:
     name: Process documentation