Do not overload operator equals on reference types

For reference types, the default implementation of the equality operator is almost always correct. By default, two references are equal only if they point to the same object.

A public or nested public reference type overloads the equality operator.

To fix a violation of this rule, remove the implementation of the equality operator.

It is safe to suppress a warning from this rule when the reference type behaves like a built-in value type. If it is meaningful to do addition or subtraction on instances of the type, it is probably correct to implement the equality operator and suppress the violation.