Remove pragmas to disable mako-missing-default

cms/templates/base.html

-## xss-lint: disable=mako-missing-default
-
 ## coding=utf-8
+## mako
 
 ## Pages currently use v1 styling by default. Once the Pattern Library
 ## rollout has been completed, this default can be switched to v2.

cms/templates/ux/reference/fragments/course-settings.html

+<%page expression_filter="h"/>
 <script>
-    ## xss-lint: disable=mako-missing-default
 </script>
 <div class="wrapper-mast wrapper">
   <header class="mast has-subtitle">

lms/templates/main.html

-## xss-lint: disable=mako-missing-default
-
 ## coding=utf-8
 
 ## This is the main Mako template that all page templates should include.

lms/templates/ux/reference/fragments/unit-fragment.html

 ## mako
+<%page expression_filter="h"/>
 <script>
-    ## xss-lint: disable=mako-missing-default
 </script>
 
 <section class="main-container">