Fix folly Travis build caused by D17506766.

Summary:
/home/folly/folly/experimental/test/QuotientMultiSetTest.cpp:60:29: error:
missing template arguments before 'reader'
     folly::QuotientMultiSet reader(data);

Reviewed By: vitaut

Differential Revision: D17959566

fbshipit-source-id: 02fec44b3d644eea0213895aa4df70349ef7d062

folly/experimental/test/QuotientMultiSetTest.cpp

@@ -57,7 +57,7 @@ class QuotientMultiSetTest : public ::testing::Test {
     auto spBuf = buff.move();
 
     folly::StringPiece data(spBuf->coalesce());
-    folly::QuotientMultiSet reader(data);
+    folly::QuotientMultiSet<> reader(data);
 
     size_t index = 0;
     folly::QuotientMultiSet<>::Iterator iter(&reader);
@@ -143,7 +143,7 @@ TEST_F(QuotientMultiSetTest, Empty) {
   builder.close(buff);
   auto spBuf = buff.move();
   folly::StringPiece data(spBuf->coalesce());
-  folly::QuotientMultiSet reader(data);
+  folly::QuotientMultiSet<> reader(data);
 
   for (size_t idx = 0; idx < 1024; idx++) {
     uint64_t key = folly::Random::rand32(rng);