Fix cloud-init .pages so that it is ready for translators (#3013)

* add `*.md` to index.md = `index*.md`

Author: sspencerwire

docs/guides/virtualization/cloud-init/.pages

@@ -1,5 +1,5 @@
 # Navigation for the cloud-init Guide
 
 nav:
-    - ... | index.md
+    - ... | index*.md
     - ...