update documentation link

[masteradhoc]

Context

• Adjust the documentation link as per request on #299 Fixes #299

Summary

This PR can be summarized in the following changelog entry:

• Fixes the documentation link to use a shortlink. Props to @masteradhoc.

Relevant technical choices:

• -

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• go to /wp-admin/plugins.php
• check if the documentation link from the yoast plugin was changed

Relevant test scenarios

• [ ] Changes should be tested with the browser console open
• [ ] Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• [ ] Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• [ ] Changes should be tested on different browsers
• [ ] Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• [x] QA should use the same steps as above.

QA can test this PR by following these steps:

• Please check test instructions

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. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

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

Innovation

• [x] No innovation project is applicable for this PR.
• [ ] This PR falls under an innovation project. I have attached the innovation label and noted the work hours.

Fixes #