Makefile.PL: remove JSON::PP but mention Storable as requirement
Makefile.PL: remove JSON::PP but mention Storable as requirement

Since Storable is a CORE module since 5.7.3 (similar to Scalar::Util), with
dropping official support for 5.6 there is no need for bundling JSON::PP for
exotic environments without Storable and JSON::PP for testing purposes.

Who wants backport should be able to fix such an issue.

Signed-off-by: Jens Rehsack <69d49c504a9219a55b8be0f905e8fe3c32ffb57f@netbsd.org>

perl5-utils/List-MoreUtils-XS,perl5-utils/List-MoreUtils-XS