Update tests for -Zborrowck-mir -> -Zborrowck=mode migration

Author: est31

src/test/compile-fail/E0506.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // revisions: ast mir
-//[mir]compile-flags: -Z emit-end-regions -Z borrowck-mir
+//[mir]compile-flags: -Z borrowck=mir
 
 struct FancyNum {
     num: u8,
@@ -19,8 +19,7 @@ fn main() {
     let mut fancy_num = FancyNum { num: 5 };
     let fancy_ref = &fancy_num;
     fancy_num = FancyNum { num: 6 }; //[ast]~ ERROR E0506
-                                     //[mir]~^ ERROR (Mir) [E0506]
-                                     //[mir]~| ERROR (Ast) [E0506]
+                                     //[mir]~^ ERROR [E0506]
 
     println!("Num: {}, Ref: {}", fancy_num.num, fancy_ref.num);
 }

src/test/compile-fail/E0508.rs

@@ -9,13 +9,12 @@
 // except according to those terms.
 
 // revisions: ast mir
-//[mir]compile-flags: -Zborrowck-mir
+//[mir]compile-flags: -Z borrowck=mir
 
 struct NonCopy;
 
 fn main() {
     let array = [NonCopy; 1];
-    let _value = array[0];  //[ast]~ ERROR E0508
-                            //[mir]~^ ERROR (Ast) [E0508]
-                            //[mir]~| ERROR (Mir) [E0508]
+    let _value = array[0];  //[ast]~ ERROR [E0508]
+                            //[mir]~^ ERROR [E0508]
 }