Added missing using statement

Author: michalChrobot

.yamato/_run-all.yml

@@ -168,7 +168,7 @@ run_all_project_tests_desktop_standalone_2021:
 # 1) The 2021 editor will soon be out of support
 # 2) We still have the same coverage by using mac and ubuntu is used in a whole bunch of different tests, so I'm quite sure it won't lead to any bug leaks
 # 3) The solution could be to manually install libss1.1 (since image has libssl3 and this causes conflicts on 2021 editor related to dotnet versions and support). There were several threads on this topic which can be looked on
-{% if editor != "2021.3" or platform.name != "ubuntu" %}
+{% if platform.name != "ubuntu" %}
     - .yamato/desktop-standalone-tests.yml#desktop_standalone_test_{{ project.name }}_{{ platform.name }}_{{ backend }}_2021.3
 {% endif -%}
 {% endfor -%}

com.unity.netcode.gameobjects/Tests/Runtime/RpcTypeSerializationTests.cs

@@ -4,6 +4,7 @@
 using Unity.Collections;
 using Unity.Netcode.TestHelpers.Runtime;
 using UnityEngine;
+using UnityEngine.TestTools;
 using Quaternion = UnityEngine.Quaternion;
 using Vector2 = UnityEngine.Vector2;
 using Vector3 = UnityEngine.Vector3;