(wangle-test) fix double ifndef in thens.rb

Summary: Looks like a bad git merge

Test Plan: builds

Reviewed By: hannesr@fb.com

Subscribers: hannesr, net-systems@, fugalh, exa, njormrod, folly-diffs@

FB internal diff: D1649773

Tasks: 5501131

Signature: t1:1649773:1414700920:cc691283884e9654803bba3ffe78f4553194752d

folly/wangle/test/Thens.cpp

@@ -5,9 +5,6 @@
 
 #include <folly/wangle/test/Thens.h>
 
-#ifndef __clang__
-// TODO: fails to compile with clang:dev.  See task #4412111
-
 TEST(Future, thenVariants) {
   SomeClass anObject;
   Executor* anExecutor;

folly/wangle/test/thens.rb

@@ -68,9 +68,6 @@ print <<EOF
 
 #include <folly/wangle/test/Thens.h>
 
-#ifndef __clang__
-// TODO: fails to compile with clang:dev.  See task #4412111
-
 TEST(Future, thenVariants) {
   SomeClass anObject;
   Executor* anExecutor;