docs: remove unneeded (hidden) component invocations.

Author: chriskrycho

tests/dummy/app/templates/application.hbs

@@ -1,13 +1 @@
 {{outlet}}
-
-<div style='visibility: hidden; height: 0'>
-{{!--
-  Unlike the rest of this document, these two components are used as part of the
-  addon's test suite. As such, they need to be rendered. However, they must not
-  be *displayed* as part of the addon docs!
---}}
-
-{{ts-component}}
-
-{{js-importing-ts}}
-</div>