Remove #![feature(never_type)] from tests.

Also remove `never_type` the feature-gate test.

Author: Centril

src/test/codegen/enum-debug-niche-2.rs

@@ -12,8 +12,6 @@
 // CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "Placeholder",{{.*}}extraData: i64 4294967295{{[,)].*}}
 // CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "Error",{{.*}}extraData: i64 0{{[,)].*}}
 
-#![feature(never_type)]
-
 #[derive(Copy, Clone)]
 pub struct Entity {
     private: std::num::NonZeroU32,

src/test/mir-opt/uninhabited-enum.rs

@@ -1,5 +1,3 @@
-#![feature(never_type)]
-
 pub enum Void {}
 
 #[no_mangle]

src/test/ui/associated-types/associated-types-ICE-when-projecting-out-of-err.rs

@@ -21,5 +21,5 @@ trait Add<RHS=Self> {
 fn ice<A>(a: A) {
     let r = loop {};
     r = r + a;
-    //~^ ERROR the trait bound `(): Add<A>` is not satisfied
+    //~^ ERROR the trait bound `!: Add<A>` is not satisfied
 }

src/test/ui/associated-types/associated-types-ICE-when-projecting-out-of-err.stderr

@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `(): Add<A>` is not satisfied
+error[E0277]: the trait bound `!: Add<A>` is not satisfied
   --> $DIR/associated-types-ICE-when-projecting-out-of-err.rs:23:11
    |
 LL |     r = r + a;
-   |           ^ the trait `Add<A>` is not implemented for `()`
+   |           ^ the trait `Add<A>` is not implemented for `!`
 
 error: aborting due to previous error
 

src/test/ui/binding/empty-types-in-patterns.rs

@@ -1,5 +1,4 @@
 // run-pass
-#![feature(never_type)]
 #![feature(exhaustive_patterns)]
 #![feature(slice_patterns)]
 #![allow(unreachable_patterns)]

src/test/ui/borrowck/assign-never-type.rs

@@ -2,8 +2,6 @@
 
 // check-pass
 
-#![feature(never_type)]
-
 pub fn main() {
     loop {
         match None {

src/test/ui/break-while-condition.rs

@@ -1,5 +1,3 @@
-#![feature(never_type)]
-
 fn main() {
     // The `if false` expressions are simply to
     // make sure we don't avoid checking everything

src/test/ui/break-while-condition.stderr

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/break-while-condition.rs:9:20
+  --> $DIR/break-while-condition.rs:7:20
    |
 LL |           let _: ! = {
    |  ____________________^
@@ -11,7 +11,7 @@ LL | |         };
               found type `()`
 
 error[E0308]: mismatched types
-  --> $DIR/break-while-condition.rs:16:13
+  --> $DIR/break-while-condition.rs:14:13
    |
 LL | /             while false {
 LL | |                 break
@@ -22,7 +22,7 @@ LL | |             }
               found type `()`
 
 error[E0308]: mismatched types
-  --> $DIR/break-while-condition.rs:24:13
+  --> $DIR/break-while-condition.rs:22:13
    |
 LL | /             while false {
 LL | |                 return

src/test/ui/coercion/coerce-issue-49593-box-never.rs

@@ -1,6 +1,5 @@
 // check-pass
 
-#![feature(never_type)]
 #![allow(unreachable_code)]
 
 use std::error::Error;

src/test/ui/coercion/coerce-to-bang-cast.rs

@@ -1,5 +1,3 @@
-#![feature(never_type)]
-
 fn foo(x: usize, y: !, z: usize) { }
 
 fn cast_a() {