escape.d: Remove special case for `hasDualContext`

[dkorpel]

I don't get this special case, it implies that returning &this.x in a struct member with dual context is actually returning this.x. While dual context does add an extra layer of indirection to the this pointer under the hood, dip1000 shouldn't treat struct field access differently because of it. The branch is not covered by tests, and dual context is in deprecated state, so I think it's safe to remove.

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[dkorpel]

Oh, so there is a runnable test that fails without it. Let me see...