[DOC release] fix missing docs for in-element

[jenweber]

The new API docs for in-element did not render in the API docs viewer due to some stray triple backticks.

[jaredgalanis]

Thank you for this 👍

[rwjblue]

🤦‍♂

[rwjblue]

CI failure is due to missing entry in tests/docs/expected.js

$ qunit tests/docs/coverage-test.js
285TAP version 13
286ok 1 Docs coverage > classitems > No missing classitems
287not ok 2 Docs coverage > classitems > No extraneous classitems
288  ---
289  message: "If you intentionally removed a public API method, please update tests/docs/expected.js. Otherwise, documentation is missing, incorrectly formatted, or in a directory that is not watched by yuidoc. All files containing documentation must have a yuidoc class declaration."
290  severity: failed
291  actual: [
292  "in-element"
293]
294  expected: []
295  stack:     at Object.<anonymous> (/home/travis/build/emberjs/ember.js/tests/docs/coverage-test.js:33:14)
296  ...
2971..2
298# pass 1
299# skip 0
300# todo 0

[rwjblue]

I can do a patch release in the morning...