Remove unnecessary std::move

Moving a temporary object prevents copy elision, and could reduce
performance.

This fixes -Wpessimizing-move compiler warning.

Test: presubmit
Bug: 154270751
Change-Id: Ia0b02d90c239572c953007272f75900ee77c6305
diff --git a/services/camera/libcameraservice/CameraService.cpp b/services/camera/libcameraservice/CameraService.cpp
index 2d55f39..d99962d 100644
--- a/services/camera/libcameraservice/CameraService.cpp
+++ b/services/camera/libcameraservice/CameraService.cpp
@@ -1570,7 +1570,7 @@
             s << ", " << std::to_string(i);
         }
     }
-    return std::move(s.str());
+    return s.str();
 }
 
 int32_t CameraService::mapToInterface(TorchModeStatus status) {
@@ -5155,7 +5155,7 @@
     }
     if (hasAny) ret << "\n";
     ret << "]\n";
-    return std::move(ret.str());
+    return ret.str();
 }
 
 CameraService::DescriptorPtr CameraService::CameraClientManager::makeClientDescriptor(