Fix single line edit prediction detection (#23456)

#23411 introduced an "Accept" callout for single line edits, but the
logic to detect them was incorrect causing it to trigger for multiline
insertions, this PR fixes that.

Release Notes:

- N/A

crates/editor/src/display_map/block_map.rs

@@ -1757,7 +1757,6 @@ impl<'a> BlockChunks<'a> {
 pub struct StickyHeaderExcerpt<'a> {
     pub excerpt: &'a ExcerptInfo,
     pub next_excerpt_controls_present: bool,
-    // TODO az remove option
     pub next_buffer_row: Option<u32>,
 }