[SYCL][NFC] Remove multi_ptr<const void, Space>::operator multi_ptr<const void, Space> (#1702)

There is no point for a type to have a conversion operator to itself.

Author: nliber

sycl/include/CL/sycl/multi_ptr.hpp

@@ -516,12 +516,6 @@ class multi_ptr<const void, Space> {
         static_cast<elem_pointer_t>(m_Pointer));
   }
 
-  // Implicit conversion to multi_ptr<const void, Space>
-  operator multi_ptr<const void, Space>() const {
-    using ptr_t = typename detail::PtrValueType<const void, Space>::type *;
-    return multi_ptr<const void, Space>(reinterpret_cast<ptr_t>(m_Pointer));
-  }
-
 private:
   pointer_t m_Pointer;
 };