chore: Fix violations of elided_named_lifetimes (#18330)

I compile Zed from nightly build pretty often and I've noticed that
we're getting a few hits on new rustc lint:
https://github.com/rust-lang/rust/pull/129207

Release Notes:

- N/A

crates/editor/src/display_map/crease_map.rs

@@ -69,7 +69,7 @@ impl CreaseSnapshot {
         &'a self,
         range: Range<MultiBufferRow>,
         snapshot: &'a MultiBufferSnapshot,
-    ) -> impl '_ + Iterator<Item = &'a Crease> {
+    ) -> impl 'a + Iterator<Item = &'a Crease> {
         let start = snapshot.anchor_before(Point::new(range.start.0, 0));
         let mut cursor = self.creases.cursor::<ItemSummary>(snapshot);
         cursor.seek(&start, Bias::Left, snapshot);