language: Remove buffer fingerprinting (#9007)

Followup to #9005 that actually removes buffer fingerprinting.

Release Notes:

- N/A

crates/copilot/src/copilot.rs

@@ -1263,7 +1263,6 @@ mod tests {
             &self,
             _: BufferId,
             _: &clock::Global,
-            _: language::RopeFingerprint,
             _: language::LineEnding,
             _: Option<std::time::SystemTime>,
             _: &mut AppContext,