phpstan: fix phpstan error

[datamweb]

Description
see https://github.com/codeigniter4/shield/actions/runs/6600355638/job/17930257377

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

[datamweb]

@kenjis I suggest that we use Schedule in GitHubAction. This makes us realize faster that the tests have failed. Not that we have to wait for a PR to be established and find out.
Using Schedule makes our code constantly tested, it makes the contributors less involved.

The disadvantages of receiving notifications are many, of course, they can be changed according to the application settings (for example, run every two days, etc.)

More info see

[kenjis]

In my opinion, since we are using GitHub for free, I would like to avoid increasing the load as much as possible.

While development is active, I don't think it will be much of a problem. This PR was also resolved fairly quickly.

However, yes, there is certainly a possibility that problems will be left unaddressed if a new PR is not forthcoming.