remove a test that does not work any more

src/test/ui/issues/issue-49955-2.rs

@@ -1,19 +0,0 @@
-// run-pass
-// compile-flags: -Z borrowck=mir
-
-use std::cell::Cell;
-
-const FIVE: Cell<i32> = Cell::new(5);
-
-#[inline(never)]
-fn tuple_field() -> &'static u32 {
-    // This test is MIR-borrowck-only because the old borrowck
-    // doesn't agree that borrows of "frozen" (i.e., without any
-    // interior mutability) fields of non-frozen temporaries,
-    // should be promoted, while MIR promotion does promote them.
-    &(FIVE, 42).1
-}
-
-fn main() {
-    assert_eq!(tuple_field().to_string(), "42");
-}