fix: PHP 8.4 deprecation notice - implicit nullable parameters

[michalbundyra]

Fixes #83

Drop Closure typehint on MockDisabler constructor (compatibility class for PHPUnit 7-9 only)

See also: php-mock/php-mock/pull/61

[michalbundyra]

@Alexander-Yi would you be able to give it a go with this change? I believe it should work.
Weird, that this deprecation notice has not been reported in our tests, as we are testing PHPUnit 9 on PHP 8.4.
I would need to check it, but can't now. So if you would be able to check and confirm if this change work I can drop a new fix release soon (in the morning?). Thanks

[Alexander-Yi]

@Alexander-Yi would you be able to give it a go with this change? I believe it should work. Weird, that this deprecation notice has not been reported in our tests, as we are testing PHPUnit 9 on PHP 8.4. I would need to check it, but can't now. So if you would be able to check and confirm if this change work I can drop a new fix release soon (in the morning?). Thanks

I really appreciate your prompt response. I gave it a go and it works well.