Use std::shuffle rather than std::random_shuffle

Summary: Because the latter was removed in C++17, and MSVC no longer supports it.

Reviewed By: yfeldblum

Differential Revision: D9565195

fbshipit-source-id: 7603ac5280ccf540abec296c7c76a43142581eb3

folly/experimental/test/EventCountTest.cpp

@@ -93,7 +93,7 @@ TEST(EventCount, Simple) {
   VLOG(1) << "Using " << ops.size() << " threads: uppers=" << uppers
           << " downers=" << downers << " sem_count=" << count;
 
-  std::random_shuffle(ops.begin(), ops.end());
+  std::shuffle(ops.begin(), ops.end(), std::mt19937(std::random_device()()));
 
   std::vector<std::thread> threads;
   threads.reserve(ops.size());

folly/stats/test/TDigestTest.cpp

@@ -134,7 +134,8 @@ TEST(TDigest, MergeLargeAsDigests) {
     values.push_back(i);
   }
   // Ensure that the values do not monotonically increase across digests.
-  std::random_shuffle(values.begin(), values.end());
+  std::shuffle(
+      values.begin(), values.end(), std::mt19937(std::random_device()()));
   for (int i = 0; i < 10; ++i) {
     std::vector<double> unsorted_values(
         values.begin() + (i * 100), values.begin() + (i + 1) * 100);