Minor documentation fixes

[jrfnl]

Minor documentation fix

The underlying Hook\HookStorage::hookPriority() function has a return type of bool|int, so this function should have the same return type.

This is also in line with the WP native return type and with the sister function Brain\Monkey\Filters\has().

Refs:

• https://developer.wordpress.org/reference/functions/has_action/
• https://developer.wordpress.org/reference/functions/has_filter/

More minor documentation fixes