Fix typo in coments for SharedMutex

Summary: Simple typo that I spotted.

Differential Revision: D23963553

fbshipit-source-id: 018e81c4878f4cb27b6676e88278d47d38706ed4

folly/experimental/coro/SharedMutex.h

@@ -80,7 +80,7 @@ namespace coro {
 ///    }
 ///
 ///    folly::coro::Task<bool> contains(std::string value) const {
-///      auto lock = co_await mutex_.co_scoped_shared_lock();
+///      auto lock = co_await mutex_.co_scoped_lock_shared();
 ///      co_return values_.count(value) > 0;
 ///    }
 ///  };