DUPP-33 Fix scheduled republish bug

[enricobattocchi]

Context

• We want to fix a bug where HTML tags in a Custom HTML block are stripped away whem a R&R copy is republished.

Summary

This PR can be summarized in the following changelog entry:

• Fixes a bug where HTML tags in a Custom HTML block would be removed when republishing a scheduled Rewrite & Republish copy.

Relevant technical choices:

• Also removes an unnecessary wp_slash call around a WP_Post object (wp_update_post() will take care of that)

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Create a new post in the block editor
• add a Custom HTML block and insert some code with tags like script and style, e.g.:

<style>
.whatever {
   font-size: 35px;
}
</style>
<script>
alert(1);
</script>

• Publish the post
  • visit it in the front end and check that you can see the tags in the source (if you use the example above you'll also get an alert)
• create a R&R copy from that post
  • change the title and something from the content, but don't change the Custom HTML block!
• schedule republish to 2 minutes in the future
• wait ⏳
• when the copy has been republished, check the original post
  • see that the changes have been applied
  • check that the tags have not been removed

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Documentation

• I have written documentation for this change.

Quality assurance

• I have tested this code to the best of my abilities
• I have added unittests to verify the code works as intended

Fixes DUPP-33

[karlijnbok]

CR & Acceptance: 👍