Fix Travis on Mac

Summary: not sure why travis complain about this line, works fine on my mac

Test Plan: run on my mac

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D63045

table/block_test.cc

@@ -240,7 +240,7 @@ class BlockReadAmpBitmapSlowAndAccurate {
   }
 
  private:
-  std::set<std::pair<size_t, size_t>> marked_ranges_ = {};
+  std::set<std::pair<size_t, size_t>> marked_ranges_;
 };
 
 TEST_F(BlockTest, BlockReadAmpBitmap) {