docs: Add @method for when() and whenNot() in models.

[sammyskills]

Description
The when() and whenNot() conditional statements works directly with models, i.e., one does not need to call the builder() method before using it. So, they should be type-hinted in IDEs or code editors, just like others.
See https://forum.codeigniter.com/showthread.php?tid=88190&pid=411611#pid411611

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• [] User guide updated
• Conforms to style guide

[MGatner]

Looks good! Rector failure is a mistake - rerunning.

[kenjis]

@sammyskills Thank you.

We recommend git rebase instead of git merge to update PR branches.
I hope you will be able to use it.
See codeigniter4/shield#789 (comment)