Don't use the plus operator unecessarily

Summary: MSVC doesn't like this and complains about ambigious overloads.

Reviewed By: ericniebler

Differential Revision: D3107438

fb-gh-sync-id: 597ba85fdb7640b0a0fda352bf53ce31cf0e38b7
fbshipit-source-id: 597ba85fdb7640b0a0fda352bf53ce31cf0e38b7

folly/detail/ThreadLocalDetail.h

@@ -85,8 +85,9 @@ struct ElementWrapper {
 
     if (p) {
       ptr = p;
-      deleter1 =
-          +[](void* pt, TLPDestructionMode) { delete static_cast<Ptr>(pt); };
+      deleter1 = [](void* pt, TLPDestructionMode) {
+        delete static_cast<Ptr>(pt);
+      };
       ownsDeleter = false;
     }
   }