Math: removed inappropriate `constexpr` from operator!=()

Method calling another method that will possibly be done via SIMD in the
future cannot be constexpr.

src/Math/RectangularMatrix.h

@@ -161,7 +161,7 @@ template<std::size_t cols, std::size_t rows, class T> class RectangularMatrix {
          * @see Vector::operator<(), Vector::operator<=(), Vector::operator>=(),
          *      Vector::operator>()
          */
-        inline constexpr bool operator!=(const RectangularMatrix<cols, rows, T>& other) const {
+        inline bool operator!=(const RectangularMatrix<cols, rows, T>& other) const {
             return !operator==(other);
         }
 

src/Math/Vector.h

@@ -197,7 +197,7 @@ template<std::size_t size, class T> class Vector {
         }
 
         /** @brief Non-equality comparison */
-        inline constexpr bool operator!=(const Vector<size, T>& other) const {
+        inline bool operator!=(const Vector<size, T>& other) const {
             return !operator==(other);
         }