Deprecated creation of dynamic property in SniffLoader

[manchenkoff]

Q	A
Bug report?	no
Feature request?	no
Library version	2.11.0

Installed library on a fresh PHP project and got these warnings:

PHP Deprecated:  Creation of dynamic property SlevomatCodingStandard\Sniffs\TypeHints\DeclareStrictTypesSniff::$newlinesCountBeforeDeclare is deprecated in /.../vendor/nunomaduro/phpinsights/src/Domain/InsightLoader/SniffLoader.php on line 40

Everything still works, but wanted to let you know in case it is possible to fix the warning.

[Jibbarth]

Will be fixed with #697