Enable Net 7 and Net 8 style rules.

OpenRA.Mods.Common/Lint/CheckTraitLocation.cs

@@ -31,7 +31,7 @@ namespace OpenRA.Mods.Common.Lint
 					{
 						// Remove the "Info" suffix.
 						var traitName = traitInfo.GetType().Name;
-						traitName = traitName.Remove(traitName.Length - 4);
+						traitName = traitName[..^4];
 						var locations = traitLocation.SystemActors.ToString().Replace(", ", " or ");
 						emitError($"`{traitName}` does not belong on `{actorInfo.Key}`. It is a system trait meant for {locations}.");
 					}