Unable to exit code block at the end of a page edited with the content editor

Summary

Writing in the content editor (Wiki editor) you can create a code block. However, if that code block is the last content node on a page, there is no way to exit that code block and return to typing normal text content.

Steps to reproduce

1. Edit a wiki page using the content editor
2. Create a code block at the end of the page, there can be no empty lines after
3. Type some code
4. Try to exit the code block

What is the current bug behavior?

The supported way to exit the code block is by using Cmd/Ctrl + return but that also submits the form on the page and exits the editing session. This is a conflicting shortcut, made even worse by a bug that submits the form without any of the changes made in the content editor: #334191 (closed)

What is the expected correct behavior?

There should be a way to exit typing the code block without resorting to keyboard shortcuts. Proposal from the comments is Shift + Return.

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

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`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

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(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes