Fix address sanitizer issue (#323)

Worked this with @cketcham2333 ...

Prior to this change, if I compile `test_core` with address sanitization
support, I got these errors below. And after this PR, these errors go
away. It's unclear if these errors would impact us under normal
conditions or not because normally `Scalar` is a primitive type that
does not have a destructor.

Author: bmhowe23

libs/core/lib/tensor_impls/xtensor_impl.cpp

@@ -97,7 +97,7 @@ class xtensor : public cudaqx::details::tensor_impl<Scalar> {
     auto size = std::accumulate(shape.begin(), shape.end(), 1,
                                 std::multiplies<size_t>());
     if (m_data)
-      std::free(m_data);
+      delete[] m_data;
 
     m_data = new Scalar[size];
     std::copy(d, d + size, m_data);
@@ -306,7 +306,7 @@ class xtensor : public cudaqx::details::tensor_impl<Scalar> {
   /// @brief Destructor for xtensor
   ~xtensor() {
     if (ownsData)
-      delete m_data;
+      delete[] m_data;
   }
 };