Remove MSVC workaround in ApplyTupleTest (#898)

Summary:
Problem:
- There was a bug in a much older version of MSVC relating to
  accessing functions in an anonymous namespace with the workaround
  being to have an extra anonymous namespace.

Solution:
- Remove the workaround as the MSVC versions that Folly now targets
  (MSVC 2015 and MSVC 2017) should not have this bug.
Pull Request resolved: https://github.com/facebook/folly/pull/898

Reviewed By: aary

Differential Revision: D9176601

Pulled By: yfeldblum

fbshipit-source-id: 7db87d28f8968eb5b3ff9d9375777f997b060a59

folly/functional/test/ApplyTupleTest.cpp

@@ -23,10 +23,6 @@
 #include <array>
 #include <memory>
 
-// this placates visual studio stupidity - see
-// http://stackoverflow.com/questions/5503901
-namespace {}
-
 namespace {
 
 void func(int a, int b, double c) {