chore(feature-flags): remove PM24032_NewNavigationPremiumUpgradeButton flag

Author: sbrown-livefront

src/Core/Constants.cs

@@ -203,7 +203,6 @@ public static class FeatureFlagKeys
     public const string EnableAutofillTriage = "enable-autofill-triage";
 
     /* Billing Team */
-    public const string PM24032_NewNavigationPremiumUpgradeButton = "pm-24032-new-navigation-premium-upgrade-button";
     public const string PM23713_PremiumBadgeOpensNewPremiumUpgradeDialog = "pm-23713-premium-badge-opens-new-premium-upgrade-dialog";
     public const string PM26793_FetchPremiumPriceFromPricingService = "pm-26793-fetch-premium-price-from-pricing-service";