Don't manually load translation files

[donnapep]

Resolves failing unit tests with the following message:

PHP Notice:  Function _load_textdomain_just_in_time was called <strong>incorrectly</strong>. Translation loading for the <code>***-lms</code> domain was triggered too early. This is usually an indicator for some code in the plugin or theme running too early. Translations should be loaded at the <code>init</code> action or later. Please see <a href="https://developer.wordpress.org/advanced-administration/debug/debug-wordpress/">Debugging in WordPress</a> for more information. (This message was added in version 6.7.0.)

Also resolves failing e2e tests.

Proposed Changes

As per the docs, it's no longer necessary to manually load translation files. As all of Sensei's translation files now exist on translate.wordpress.org, I think we can get rid of the code to load translations.

Testing Instructions

1. Disable all other plugins except Sensei.
2. On trunk, set the site language to anything other than English.
3. Download language packs if necessary.
4. Ensure that Sensei is translated.
5. Switch to this branch.
6. Ensure that Sensei is still translated.
7. Check that the above notice is not displayed in the logs (note that I wasn't able to get it to appear in the logs prior to this change).

Deprecated Code

• load_localisation
• load_plugin_textdomain

Pre-Merge Checklist

• PR title and description contain sufficient detail and accurately describe the changes
• Adheres to coding standards (PHP, JavaScript, CSS, HTML)
• All strings are translatable (without concatenation, handles plurals)
• Follows our naming conventions (P6rkRX-4oA-p2)
• Hooks (p6rkRX-1uS-p2) and functions are documented
• New UIs are responsive and use a mobile-first approach
• Code is tested on the minimum supported PHP and WordPress versions

[github-actions]

Test the previous changes of this PR with WordPress Playground.

[github-actions]

Test the previous changes of this PR with WordPress Playground.

[github-actions]

Test the previous changes of this PR with WordPress Playground.

[github-actions]

Test the previous changes of this PR with WordPress Playground.

[m1r0]

Translations are working as before. 👍