scbuild: update stub method for isV261Active

The version has been created, so we can fix this function now.

Release note: None

Author: rafiss

pkg/sql/schemachanger/scbuild/internal/scbuildstmt/process.go

@@ -229,6 +229,5 @@ var isV254Active = func(_ tree.NodeFormatter, _ sessiondatapb.NewSchemaChangerMo
 }
 
 var isV261Active = func(_ tree.NodeFormatter, _ sessiondatapb.NewSchemaChangerMode, activeVersion clusterversion.ClusterVersion) bool {
-	// change the cluster version once V26_1 is created
-	return activeVersion.IsActive(clusterversion.V25_4)
+	return activeVersion.IsActive(clusterversion.V26_1)
 }