Remove DAM annotations from enum converter

[LakshanF]

Remove DAM annotations from Enum converter since the trimmer always preserve enums.

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[sbomer]

LGTM but I'd appreciate if @MichalStrehovsky could take a look too.

[MichalStrehovsky]

Looks good from trimming perspective. Can't talk about TypeConverter or why we accept System.Enum (and whether this should accept all non-enums for the same reasons it accepts System.Enum).

[MichalStrehovsky]

I'm a little bit concerned we have tests where this is used with a non-enum and it apparently works (System.Enum is really no different from just System.Object, or whatever).