Fix folly/gen/test/ParallelMapTest.cpp under MSVC

Summary:
[Folly] Fix `folly/gen/test/ParallelMapTest.cpp` under MSVC, which does not appear automatically to deduce `{"str"}` as `std::initializer_list<char const*>`.

Breakage in {D14625210}.

Reviewed By: luciang

Differential Revision: D14663535

fbshipit-source-id: 092786236c6589790f234741e52b3fc045bd2b0e

folly/gen/test/ParallelMapTest.cpp

@@ -156,7 +156,8 @@ TEST(Pmap, Rvalues) {
 }
 
 TEST(Pmap, Exception) {
-  EXPECT_THROW(from({"a"}) | pmap(To<int>()) | count, std::runtime_error);
+  std::vector<char const*> input{"a"};
+  EXPECT_THROW(from(input) | pmap(To<int>()) | count, std::runtime_error);
 }
 
 int main(int argc, char* argv[]) {