Update strings.stderr

Author: yaahc

tests/ui/strings.stderr

@@ -53,10 +53,10 @@ error: you added something to a string. Consider using `String::push_str()` inst
    |             ^^^^^^^^^
 
 error: manual implementation of an assign operation
-  --> $DIR/strings.rs:65:7
+  --> $DIR/strings.rs:54:7
    |
-65 |     ; x = x + 1;
+54 |     ; x = x + 1;
    |       ^^^^^^^^^ help: replace it with: `x += 1`
 
-error: aborting due to 11 previous errors
+error: aborting due to 9 previous errors