D2L0030 wording is specific to Mutability, but is used for Statics

> Something I've noticed:
> `error D2L0030: There is a Mutability.Audited or Mutability.Unaudited attribute on an immutable member. Remove the unnecessary attribute.`
> On a `Statics.Unaudited`. Might be worth changing the message at some point to include Statics., or making it more generic.
> - @TimothyJCowen 