Remove the duplicate ipv6Firewall V5 tag (Azure#24352)

Author: LeiWang3

specification/sql/resource-manager/readme.md

@@ -955,7 +955,6 @@ input-file:
 - ./Microsoft.Sql/preview/2021-05-01-preview/ServerConnectionPolicies.json
 - ./Microsoft.Sql/preview/2021-11-01-preview/DistributedAvailabilityGroups.json
 - ./Microsoft.Sql/preview/2021-11-01-preview/ServerTrustCertificates.json
-- ./Microsoft.Sql/preview/2021-11-01-preview/IPv6FirewallRules.json
 - ./Microsoft.Sql/preview/2021-11-01-preview/EndpointCertificates.json
 - ./Microsoft.Sql/preview/2020-11-01-preview/ManagedDatabaseSensitivityLabels.json
 - ./Microsoft.Sql/preview/2020-11-01-preview/SensitivityLabels.json