Remove restriction in FindWrapSystemPCRE2.cmake to only look for Config packages

FindWrapSystemPCRE2.cmake has

find_package(PCRE2 COMPONENTS 16BIT ${${CMAKE_FIND_PACKAGE_NAME}_FIND_VERSION} CONFIG QUIET)

Note the CONFIG.

This prevents finding a FindPCRE2.cmake file if one exists.

One particular use case of this is building Qt with 3rd party dependencies provided by Conan, where Conan would generate its own FindPCRE2.cmake file when using the 'cmake_find_package' generator.

It's probably possible to tell Conan to generate a Config.cmake file instead, but I don't see a reason why we should restricting the search to CONFIG files only.

This would be a slight behavior change, and might cause some issues in case if the FindPCRE2.cmake is broken (we've had multiple issues we had to work around with harfbuzz config files for example).