[DOC release-3-20-1] fix missing docs

[ci skip]

(cherry picked from commit 863cca5)

Author: jenweber

packages/@ember/-internals/glimmer/lib/syntax/in-element.ts

@@ -30,8 +30,6 @@
  `destinationElement`. Passing `null` changes the behaviour to appended at the end
  of any existing content. Any other value than `null` is currently not supported.
 
- ```
-
  @method in-element
  @for Ember.Templates.helpers
  @public

tests/docs/expected.js

@@ -276,6 +276,7 @@ module.exports = {
     'href',
     'htmlSafe',
     'if',
+    'in-element',
     'includes',
     'incrementProperty',
     'indexOf',