aos_squared is std::pair (#162)

Author: jwaldrop107

include/simde/types.hpp

@@ -99,7 +99,7 @@ using braket = chemist::braket::BraKet<BraType, OpType, KetType>;
 using aos = chemist::wavefunction::AOs;
 
 /// Typedef of the class used to represent a product of atomic orbital spaces
-using aos_squared = utilities::dsl::Multiply<aos, aos>;
+using aos_squared = std::pair<aos, aos>;
 
 /// Typedef of the class used to represent transformed AOs
 using mos = chemist::wavefunction::MOs;