rustfmt: Use show_parse_errors

`rustfmt` gives warning:

 Warning: the `hide_parse_errors` option is deprecated. Use
 `show_parse_errors` instead

As suggested use `show_parse_errors` and switch the boolean value.

Author: tcharding

rustfmt.toml

@@ -70,7 +70,7 @@ color = "Auto"
 unstable_features = false
 disable_all_formatting = false
 skip_children = false
-hide_parse_errors = false
+show_parse_errors = true
 error_on_line_overflow = false
 error_on_unformatted = false
 emit_mode = "Files"