Remove deprecated copilot event (#18862)

`CopilotEvent` was succeeded by `InlineCompletionEvent` 5 months ago.

Release Notes:

- N/A

crates/telemetry_events/src/telemetry_events.rs

@@ -91,7 +91,6 @@ impl Display for AssistantPhase {
 #[serde(tag = "type")]
 pub enum Event {
     Editor(EditorEvent),
-    Copilot(CopilotEvent), // Needed for clients sending old copilot_event types
     InlineCompletion(InlineCompletionEvent),
     Call(CallEvent),
     Assistant(AssistantEvent),
@@ -121,15 +120,6 @@ pub struct EditorEvent {
     pub is_via_ssh: bool,
 }
 
-/// Deprecated since Zed v0.137.0 (2024-05-29). Replaced by InlineCompletionEvent.
-// Needed for clients sending old copilot_event types
-#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
-pub struct CopilotEvent {
-    pub suggestion_id: Option<String>,
-    pub suggestion_accepted: bool,
-    pub file_extension: Option<String>,
-}
-
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
 pub struct InlineCompletionEvent {
     /// Provider of the completion suggestion (e.g. copilot, supermaven)