Remove println!'s from ui/issues/issue-52126-assign-op-invariance.rs

This is not strictly necessary to make this test "more robust with
respect to NLL"; its just an attempt to narrow the scope of the test
and focus on its core.

src/test/ui/issues/issue-52126-assign-op-invariance.nll.stderr

@@ -3,9 +3,9 @@ error[E0597]: `line` does not live long enough
    |
 LL |         let v: Vec<&str> = line.split_whitespace().collect();
    |                            ^^^^ borrowed value does not live long enough
-LL |         //~^ ERROR `line` does not live long enough
-LL |         println!("accumulator before add_assign {:?}", acc.map);
-   |                                                        ------- borrow used here, in later iteration of loop
+...
+LL |         acc += cnt2;
+   |         --- borrow used here, in later iteration of loop
 ...
 LL |     }
    |     - `line` dropped here while still borrowed

src/test/ui/issues/issue-52126-assign-op-invariance.rs

@@ -43,7 +43,7 @@ pub fn panics() {
     for line in vec!["123456789".to_string(), "12345678".to_string()] {
         let v: Vec<&str> = line.split_whitespace().collect();
         //~^ ERROR `line` does not live long enough
-        println!("accumulator before add_assign {:?}", acc.map);
+        // println!("accumulator before add_assign {:?}", acc.map);
         let mut map = HashMap::new();
         for str_ref in v {
             let e = map.entry(str_ref);
@@ -53,7 +53,7 @@ pub fn panics() {
         }
         let cnt2 = Counter{map};
         acc += cnt2;
-        println!("accumulator after add_assign {:?}", acc.map);
+        // println!("accumulator after add_assign {:?}", acc.map);
         // line gets dropped here but references are kept in acc.map
     }
 }