Clean up edit predictions settings (#24692)

This PR does some clean up for the edit predictions settings:

- Removed `editor.show_edit_predictions_in_menu`
- Renamed `edit_predictions.inline_preview` to `edit_predictions.mode`

Release Notes:

- N/A

---------

Co-authored-by: Agus Zubiaga <agus@zed.dev>

assets/settings/default.json

@@ -168,9 +168,6 @@
   /// Whether to show the signature help after completion or a bracket pair inserted.
   /// If `auto_signature_help` is enabled, this setting will be treated as enabled also.
   "show_signature_help_after_edits": false,
-  /// Whether to show the edit predictions next to the completions provided by a language server.
-  /// Only has an effect if edit prediction provider supports it.
-  "show_edit_predictions_in_menu": true,
   // Whether to show wrap guides (vertical rulers) in the editor.
   // Setting this to true will show a guide at the 'preferred_line_length' value
   // if 'soft_wrap' is set to 'preferred_line_length', and will show any
@@ -795,11 +792,11 @@
     ],
     // When to show edit predictions previews in buffer.
     // This setting takes two possible values:
-    // 1. Display inline when there are no language server completions available.
-    //     "inline_preview": "auto"
-    // 2. Display inline when holding modifier key (alt by default).
-    //     "inline_preview": "when_holding_modifier"
-    "inline_preview": "auto"
+    // 1. Display inline when holding modifier key (alt by default).
+    //     "mode": "auto"
+    // 2. Display inline when there are no language server completions available.
+    //     "mode": "eager_preview"
+    "mode": "auto"
   },
   // Settings specific to journaling
   "journal": {