Remove test that tested behavior of unchecked blocks

We don't have unchecked blocks anymore.

src/test/compile-fail/borrowck-unchecked-with-borrow.rs

@@ -1,34 +0,0 @@
-// xfail-test
-// xfail-fast
-#[legacy_modes];
-
-fn impure(_i: int) {}
-
-// check that unchecked alone does not override borrowck:
-fn foo(v: &const Option<int>) {
-    match *v {
-      Some(ref i) => {
-        //~^ ERROR illegal borrow unless pure
-        unsafe {
-            impure(*i); //~ NOTE impure due to access to impure function
-        }
-      }
-      None => {
-      }
-    }
-}
-
-fn bar(v: &const Option<int>) {
-    match *v {
-      Some(ref i) => {
-        unsafe {
-            impure(*i);
-        }
-      }
-      None => {
-      }
-    }
-}
-
-fn main() {
-}