feature_flags: Do not enable feature flags by default in dev builds (#27065)

Closes #ISSUE

Release Notes:

- N/A

crates/feature_flags/src/feature_flags.rs

@@ -207,7 +207,7 @@ impl FeatureFlagAppExt for App {
     fn has_flag<T: FeatureFlag>(&self) -> bool {
         self.try_global::<FeatureFlags>()
             .map(|flags| flags.has_flag::<T>())
-            .unwrap_or_else(|| T::enabled_in_development())
+            .unwrap_or(false)
     }
 
     fn is_staff(&self) -> bool {