Fix source code issues found by clang from toolchain/dev branch

Summary:
To fix source issues that result in compilation error:

error: a template argument list is expected after a name prefixed by the template keyword [-Wmissing-template-arg-list-after-template-kw]

Reviewed By: thevinster

Differential Revision: D58050664

fbshipit-source-id: bba199f79afab238408568c21315362742875ff5

Author: yozhu

fatal/type/call_traits.h

@@ -163,7 +163,7 @@ class call_operator_traits {
    */
   template <typename T, typename... Args>
   using supports = decltype(
-    is_impl<Args...>::template sfinae(static_cast<T *>(nullptr))
+    is_impl<Args...>::template sfinae<>(static_cast<T *>(nullptr))
   );
 };
 
@@ -226,7 +226,7 @@ class call_operator_traits {
       struct bind { \
         template <typename... UArgs> \
         using supports = decltype( \
-          member_fn_supports_impl<UArgs...>::template sfinae( \
+          member_fn_supports_impl<UArgs...>::template sfinae<>( \
             static_cast<typename ::std::remove_reference<U>::type *>(nullptr) \
           ) \
         ); \