Update USP0022.md

doc/USP0022.md

@@ -1,4 +1,4 @@
-# USP0022 Prefer reference equality
+# USP0022 Unity objects should not use if null coalescing
 
 We have a dedicated diagnostic `UNT0029` to prevent is-null check with `UnityEngine.Object`. But `IDE0270` will suggest to use is-null check over reference equality method.