Remove more obsolete test flags

Author: oli-obk

src/test/ui/binding/func-arg-ref-pattern.rs

@@ -1,5 +1,4 @@
 // run-pass
-// exec-env:RUST_POISON_ON_FREE=1
 
 // Test argument patterns where we create refs to the inside of
 // boxes. Make sure that we don't free the box as we match the

src/test/ui/issues/issue-34932.rs

@@ -1,6 +1,5 @@
 // run-pass
 // compile-flags:--test
-// rustc-env:RUSTC_BOOTSTRAP_KEY=
 #![cfg(any())] // This test should be configured away
 #![feature(rustc_attrs)] // Test that this is allowed on stable/beta
 #![feature(iter_arith_traits)] // Test that this is not unused

src/test/ui/mismatched_types/const-fn-in-trait.rs

@@ -1,5 +1,3 @@
-// rustc-env:RUST_NEW_ERROR_FORMAT
-
 #![feature(const_fn)]
 
 trait Foo {

src/test/ui/mismatched_types/trait-impl-fn-incompatibility.rs

@@ -1,5 +1,3 @@
-// rustc-env:RUST_NEW_ERROR_FORMAT
-
 trait Foo {
     fn foo(x: u16);
     fn bar(&mut self, bar: &mut Bar);