Remove unreferenced FF (#6612)

Author: amorask-bitwarden

src/Core/Constants.cs

@@ -186,7 +186,6 @@ public static class FeatureFlagKeys
 
     /* Billing Team */
     public const string TrialPayment = "PM-8163-trial-payment";
-    public const string PM19422_AllowAutomaticTaxUpdates = "pm-19422-allow-automatic-tax-updates";
     public const string PM21821_ProviderPortalTakeover = "pm-21821-provider-portal-takeover";
     public const string PM22415_TaxIDWarnings = "pm-22415-tax-id-warnings";
     public const string PM25379_UseNewOrganizationMetadataStructure = "pm-25379-use-new-organization-metadata-structure";