Check for predict-edits feature flag, remove is_staff check (#23165)

Release Notes:

- N/A

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>

crates/feature_flags/src/feature_flags.rs

@@ -59,9 +59,9 @@ impl FeatureFlag for ToolUseFeatureFlag {
     }
 }
 
-pub struct ZetaFeatureFlag;
-impl FeatureFlag for ZetaFeatureFlag {
-    const NAME: &'static str = "zeta";
+pub struct PredictEditsFeatureFlag;
+impl FeatureFlag for PredictEditsFeatureFlag {
+    const NAME: &'static str = "predict-edits";
 }
 
 pub struct GitUiFeatureFlag;