Add explicit nullable to Preg::replaceCallbackStrictGroups for PHP 8.4 compatibility

[GromNaN]

Explicit nullable type have been added to the branch 2.x in 28fb502, then merged into main.
But the method Preg::replaceCallbackStrictGroups was introduced in version 3.x (main branch) by 317c8a5

This is the last occurrence.

$ php -l **/*.php
No syntax errors detected in ./tests/RegexTests/ReplaceCallbackTest.php
No syntax errors detected in ./tests/RegexTests/MatchAllTest.php
No syntax errors detected in ./tests/RegexTests/ReplaceCallbackArrayTest.php
No syntax errors detected in ./tests/RegexTests/ReplaceTest.php
No syntax errors detected in ./tests/RegexTests/MatchWithOffsetsTest.php
No syntax errors detected in ./tests/RegexTests/MatchTest.php
No syntax errors detected in ./tests/RegexTests/MatchAllWithOffsetsTest.php
No syntax errors detected in ./tests/RegexTests/IsMatchTest.php
No syntax errors detected in ./tests/PregTests/ReplaceCallbackTest.php
No syntax errors detected in ./tests/PregTests/MatchAllTest.php
No syntax errors detected in ./tests/PregTests/ReplaceCallbackArrayTest.php
No syntax errors detected in ./tests/PregTests/IsMatchWithOffsetsTest.php
No syntax errors detected in ./tests/PregTests/ReplaceTest.php
No syntax errors detected in ./tests/PregTests/SplitTest.php
No syntax errors detected in ./tests/PregTests/IsMatchAllTest.php
No syntax errors detected in ./tests/PregTests/GrepTest.php
No syntax errors detected in ./tests/PregTests/MatchTest.php
No syntax errors detected in ./tests/PregTests/IsMatchAllWithOffsetsTest.php
No syntax errors detected in ./tests/PregTests/SplitWithOffsetsTest.php
No syntax errors detected in ./tests/PregTests/IsMatchTest.php
No syntax errors detected in ./tests/phpstan-locate-phpunit-autoloader.php
No syntax errors detected in ./tests/BaseTestCase.php
No syntax errors detected in ./src/MatchResult.php
No syntax errors detected in ./src/Regex.php
No syntax errors detected in ./src/MatchAllWithOffsetsResult.php
No syntax errors detected in ./src/MatchWithOffsetsResult.php
No syntax errors detected in ./src/MatchAllStrictGroupsResult.php
No syntax errors detected in ./src/UnexpectedNullMatchException.php
No syntax errors detected in ./src/MatchStrictGroupsResult.php
No syntax errors detected in ./src/MatchAllResult.php
No syntax errors detected in ./src/ReplaceResult.php
PHP Deprecated:  Composer\Pcre\Preg::replaceCallbackStrictGroups(): Implicitly marking parameter $count as nullable is deprecated, the explicit nullable type must be used instead in ./src/Preg.php on line 206

Deprecated: Composer\Pcre\Preg::replaceCallbackStrictGroups(): Implicitly marking parameter $count as nullable is deprecated, the explicit nullable type must be used instead in ./src/Preg.php on line 206
No syntax errors detected in ./src/Preg.php
No syntax errors detected in ./src/PcreException.php

[Seldaek]

Oh good catch thanks