Allow serialising already-blessed bools

[ccakes]

graphql-perl/lib/GraphQL/Type/Scalar.pm

Line 179 in 48ba8eb

serialize => _leave_undef(sub { !is_Bool($_[0]) and die "Not a Boolean.\n"; $_[0] ? JSON->true : JSON->false }),

I'm trying to wire up a method to a GraphQL field that returns already-blessed JSON::PP::Boolean instances which was tripping up ☝️ this check.

This PR just allows serialising objects that pass the JSON::is_bool test

[coveralls]

Pull Request Test Coverage Report for Build 400

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 90.986%

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Totals
Change from base Build 397:	0.0%
Covered Lines:	1181
Relevant Lines:	1298

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💛 - Coveralls

[mohawk2]

Great work, thanks!

[mohawk2]

Released as 0.44.