VariantType: Fix typo in VARIANT_TYPE_BYTESTRING_ARRAY.

* gio/src/varianttype.ccg: VARIANT_TYPE_BYTESTRING_ARRAY was set
  to G_VARIANT_TYPE_STRING_ARRAY instead of
  G_VARIANT_TYPE_BYTESTRING_ARRAY, causing VariantDict::lookup_value()
  to fail on an array of filenames when given a vector<std::string>.