Use new multibuffer excerpts in project search (#27893)

Follow-up of https://github.com/zed-industries/zed/pull/27876
Closes https://github.com/zed-industries/zed/issues/13513

Release Notes:

- Improved multi buffer excerpts to merge when expanded

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Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/multi_buffer/Cargo.toml

@@ -28,7 +28,6 @@ collections.workspace = true
 ctor.workspace = true
 buffer_diff.workspace = true
 env_logger.workspace = true
-futures.workspace = true
 gpui.workspace = true
 itertools.workspace = true
 language.workspace = true