camera: fix `-Wpessimizing-move` compiler warnings

Test: add `USE_CAMERA_V4L2_HAL := true` to
      hardware/libhardware/modules/camera/3_4/Android.mk and build
      mmm hardware/libhardware/modules/camera/3_4
Change-Id: I464761128a09d90415ee6ac1ef1244391edb0b54
Signed-off-by: Sergii Piatakov <sergii.piatakov@globallogic.com>
diff --git a/modules/camera/3_4/request_tracker.cpp b/modules/camera/3_4/request_tracker.cpp
index 4168c3b..f92d254 100644
--- a/modules/camera/3_4/request_tracker.cpp
+++ b/modules/camera/3_4/request_tracker.cpp
@@ -51,7 +51,7 @@
   for (const auto& output_buffer : request.output_buffers) {
     result.insert(output_buffer.stream);
   }
-  return std::move(result);
+  return result;
 }
 
 bool RequestTracker::Add(std::shared_ptr<CaptureRequest> request) {