d3d12device: Fix typo in object name

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6549>

subprojects/gst-plugins-bad/gst-libs/gst/d3d12/gstd3d12device.cpp

@@ -279,7 +279,7 @@ private:
       idx = name_it->second;
     }
 
-    return std::string ("d3d11device") + std::to_string (adapter_index) + "-" +
+    return std::string ("d3d12device") + std::to_string (adapter_index) + "-" +
         std::to_string (idx);
   }