Fix bug in origin location computation.

In particular the second "<=" is wrong, it should be "<", since ranges are end-exclusive. For clarity just replace it with Range::contains.

src/renderer/display_list.rs

@@ -1149,7 +1149,7 @@ fn format_header<'a>(
                 ..
             } = item
             {
-                if main_range >= range.0 && main_range <= range.1 + end_line.len() {
+                if (range.0..range.1 + end_line.len()).contains(&main_range) {
                     let char_column = text[0..(main_range - range.0).min(text.len())]
                         .chars()
                         .count();