Function.h: remove FOLLY_MSVC_DISABLE_WARNING

Summary:
We recently removed declarations of Function constructors and
assignment operators that took non-const Function references. They
were necessary at the time to make sure that the templated
constructor that can take any invokable object did not get
selected for copying Functions from non-const lvalues. This,
however, is now provided by some std::enable_if construct.

Reviewed By: ericniebler

Differential Revision: D4818736

fbshipit-source-id: 08197721beef009f6ae482b576df78ec6999d132

folly/Function.h

@@ -424,9 +424,6 @@ inline auto invoke(M(C::*d), Args&&... args)
 } // namespace function
 } // namespace detail
 
-FOLLY_PUSH_WARNING
-FOLLY_MSVC_DISABLE_WARNING(4521) // Multiple copy constructors
-FOLLY_MSVC_DISABLE_WARNING(4522) // Multiple assignment operators
 template <typename FunctionType>
 class Function final : private detail::function::FunctionTraits<FunctionType> {
   // These utility types are defined outside of the template to reduce
@@ -700,7 +697,6 @@ class Function final : private detail::function::FunctionTraits<FunctionType> {
     return std::move(*this).asSharedProxy();
   }
 };
-FOLLY_POP_WARNING
 
 template <typename FunctionType>
 void swap(Function<FunctionType>& lhs, Function<FunctionType>& rhs) noexcept {