update test-cases for new for loop syntax

test/cases/compile_errors/invalid_pointer_for_var_type.zig

@@ -1,7 +1,7 @@
 extern fn ext() usize;
 var bytes: [ext()]u8 = undefined;
 export fn f() void {
-    for (bytes) |*b, i| {
+    for (&bytes, 0..) |*b, i| {
         b.* = @as(u8, i);
     }
 }

test/cases/compile_errors/underscore_should_not_be_usable_inside_for.zig

@@ -1,6 +1,6 @@
 export fn returns() void {
-    for ([_]void{}) |_, i| {
-        for ([_]void{}) |_, j| {
+    for ([_]void{}, 0..) |_, i| {
+        for ([_]void{}, 0..) |_, j| {
             return _;
         }
     }

test/cases/variable_shadowing.3.zig

@@ -1,10 +1,10 @@
 pub fn main() void {
     var i = 0;
-    for ("n") |_, i| {
+    for ("n", 0..) |_, i| {
     }
 }
 
 // error
 //
-// :3:19: error: loop index capture 'i' shadows local variable from outer scope
+// :3:24: error: capture 'i' shadows local variable from outer scope
 // :2:9: note: previous declaration here