fixing a compile error on windows

Summary:
This file only compiles with MSVC after I made the change in this diff.

The code was difficult to follow, so I am not sure if the template is needed here?

Reviewed By: yfeldblum

Differential Revision: D4656575

fbshipit-source-id: 19415623bdb1757b573f12cdc9d8544d716ce6f2

folly/Format-inl.h

@@ -270,7 +270,7 @@ void BaseFormatter<Derived, containerMode, Args...>::operator()(
           "folly::format: may not have both default and explicit arg indexes");
     }
 
-    asDerived().template doFormat(size_t(argIndex), arg, out);
+    asDerived().doFormat(size_t(argIndex), arg, out);
   }
 }