kill dep-graph-unrelated test

Doesnt' seem to add much value, and since we don't track
`TransCrateItem` anymore, it's not clear what to translate it to.

src/test/compile-fail/dep-graph-unrelated.rs

@@ -1,22 +0,0 @@
-// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// Test that two unrelated functions have no trans dependency.
-
-// compile-flags: -Z query-dep-graph
-
-#![feature(rustc_attrs)]
-#![allow(dead_code)]
-
-#[rustc_if_this_changed]
-fn main() { }
-
-#[rustc_then_this_would_need(TransCrateItem)] //~ ERROR no path from `main`
-fn bar() { }