edit predictions: Fix docs for enabled_in_assistant (#25770)

Remove mention of "prompt editor" since that feature isn't out yet.

Release Notes:

- N/A

crates/language/src/language_settings.rs

@@ -236,7 +236,7 @@ pub struct EditPredictionSettings {
     pub mode: EditPredictionsMode,
     /// Settings specific to GitHub Copilot.
     pub copilot: CopilotSettings,
-    /// Whether edit predictions are enabled in the assistant prompt editor.
+    /// Whether edit predictions are enabled in the assistant panel.
     /// This setting has no effect if globally disabled.
     pub enabled_in_assistant: bool,
 }