remove a custom implementation of std::enable_if

googletest/include/gtest/internal/gtest-internal.h

@@ -991,13 +991,6 @@ struct IsRecursiveContainerImpl<C, true> {
 template <typename C>
 struct IsRecursiveContainer : public IsRecursiveContainerImpl<C>::type {};
 
-// EnableIf<condition>::type is void when 'Cond' is true, and
-// undefined when 'Cond' is false.  To use SFINAE to make a function
-// overload only apply when a particular expression is true, add
-// "typename EnableIf<expression>::type* = 0" as the last parameter.
-template<bool> struct EnableIf;
-template<> struct EnableIf<true> { typedef void type; };  // NOLINT
-
 // Utilities for native arrays.
 
 // ArrayEq() compares two k-dimensional native arrays using the