Bless output of test nll/get_default.rs for Polonius

2 of the 3 errors are "fixed by Polonius" 🎉

src/test/ui/nll/get_default.polonius.stderr

@@ -0,0 +1,15 @@
+error[E0502]: cannot borrow `*map` as mutable because it is also borrowed as immutable
+  --> $DIR/get_default.rs:32:17
+   |
+LL |         match map.get() {
+   |               --- immutable borrow occurs here
+LL |             Some(v) => {
+LL |                 map.set(String::new()); // Both AST and MIR error here
+   |                 ^^^ mutable borrow occurs here
+LL |
+LL |                 return v;
+   |                        - immutable borrow later used here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0502`.