Blind attempt to fix MSVC pgcrypto build.

Commit db7d1a7b0 pulled out Mkvcbuild.pm's custom support for building
contrib/pgcrypto, but neglected to inform it that that module can now
be built normally.  Or at least I guess it can now be built normally.
But this is definitely causing bowerbird to fail, since it's trying to
test a module it hasn't built.

src/tools/msvc/Mkvcbuild.pm

@@ -47,7 +47,7 @@ my @contrib_excludes = (
 	'hstore_plperl',    'hstore_plpython',
 	'intagg',           'jsonb_plperl',
 	'jsonb_plpython',   'ltree_plpython',
-	'pgcrypto',         'sepgsql',
+	'sepgsql',
 	'brin',             'test_extensions',
 	'test_misc',        'test_pg_dump',
 	'snapshot_too_old', 'unsafe_tests');