RCS1055 for empty enums

[jnyrup]

Product and Version Used:
Using newest v4.9.0 RCS1055 is triggered on enums.
It does not trigger on class, struct or interface, which looks related to #1134.

Steps to Reproduce:

root = true

[*.cs]
dotnet_diagnostic.RCS1055.severity = error

class Class;

enum Enum; // <-- RCS1055

interface IInterface;

struct Struct;

Actual Behavior:
RCS1055 is reported.

Expected Behavior:
RCS1055 should not be reported.