Use semantic markup (modules o-p) (#6681)

* Use semantic markup.

* Use real option, not alias.

* E() now works better.

plugins/modules/pushbullet.py

@@ -59,7 +59,7 @@ options:
     url:
         type: str
         description:
-          - URL field, used when I(push_type) is C(link).
+          - URL field, used when O(push_type=link).
 
 notes:
    - Requires pushbullet.py Python package on the remote host.