docs: add @property to Time

[kenjis]

Description

• add @property

See https://codeigniter4.github.io/CodeIgniter4/libraries/time.html#getters
Related #8338

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

[kenjis]

Removed $date because it cannot be read.

        $time = Time::now();
        dd($time->date); // null

[kenjis]

@paulbalandan Why cannot we use @property-read?

The phpdoc_no_alias_tag rule replaces it.
https://cs.symfony.com/doc/rules/phpdoc/phpdoc_no_alias_tag.html