update tests for migrate mode by default

src/test/ui/liveness/liveness-assign/liveness-assign-imm-local-with-init.rs

@@ -1,16 +1,10 @@
-// revisions: ast mir
-//[mir]compile-flags: -Zborrowck=mir
-
 fn test() {
-    let v: isize = 1; //[ast]~ NOTE first assignment
-                      //[mir]~^ NOTE first assignment
-                      //[mir]~| HELP make this binding mutable
-                      //[mir]~| SUGGESTION mut v
+    let v: isize = 1; //~ NOTE first assignment
+                      //~| HELP make this binding mutable
+                      //~| SUGGESTION mut v
     v.clone();
-    v = 2; //[ast]~ ERROR cannot assign twice to immutable variable
-           //[mir]~^ ERROR cannot assign twice to immutable variable `v`
-           //[ast]~| NOTE cannot assign twice to immutable
-           //[mir]~| NOTE cannot assign twice to immutable
+    v = 2; //~ ERROR cannot assign twice to immutable variable `v`
+           //~| NOTE cannot assign twice to immutable
     v.clone();
 }