Update comment now we have accurate content widths

src/display/side_by_side.rs

@@ -199,14 +199,11 @@ impl SourceDimensions {
         // between LHS and RHS.
         //
         // Instead, cap the display width based on the maximum length
-        // of lines within the file.
+        // of visible lines within the file.
         //
-        // This is a crude heuristic because it ignores which lines of
-        // the file actually get displayed, so we can still end up
-        // with some superfluous space. It also naively assumes that
-        // byte length is the same display length, which is generally
-        // OK because byte length will tend to be larger than the
-        // display length.
+        // This naively assumes that byte length is the same as
+        // display length, which is generally OK because byte length
+        // will tend to be larger than the display length.
         let display_width = min(terminal_width, (content_max_width + 4) * 2 + SPACER.len());
 
         assert!(