Remove unused indices in mac/text_system (#40420)

just simplifying the code a bit

Release Notes:

- N/A

Co-authored-by: Cole Miller <cole@zed.dev>

crates/gpui/src/platform/mac/text_system.rs

@@ -67,7 +67,8 @@ struct MacTextSystemState {
     font_ids_by_postscript_name: HashMap<String, FontId>,
     font_ids_by_font_key: HashMap<FontKey, SmallVec<[FontId; 4]>>,
     postscript_names_by_font_id: HashMap<FontId, String>,
-    zwnjs_scratch_space: Vec<(usize, usize)>,
+    /// UTF-16 indices of ZWNJS
+    zwnjs_scratch_space: Vec<usize>,
 }
 
 impl MacTextSystem {
@@ -457,7 +458,7 @@ impl MacTextSystemState {
                 string.replace_str(&CFString::new(text), CFRange::init(utf16_start, 0));
                 if needs_zwnj {
                     let zwnjs_pos = string.char_len();
-                    self.zwnjs_scratch_space.push((n_zwnjs, zwnjs_pos as usize));
+                    self.zwnjs_scratch_space.push(zwnjs_pos as usize);
                     string.replace_str(
                         &CFString::from_static_string(ZWNJ_STR),
                         CFRange::init(zwnjs_pos, 0),
@@ -516,7 +517,7 @@ impl MacTextSystemState {
                 let mut glyph_utf16_ix = usize::try_from(glyph_utf16_ix).unwrap();
                 let r = self
                     .zwnjs_scratch_space
-                    .binary_search_by(|&(_, it)| it.cmp(&glyph_utf16_ix));
+                    .binary_search_by(|&it| it.cmp(&glyph_utf16_ix));
                 match r {
                     // this glyph is a ZWNJ, skip it
                     Ok(_) => continue,