Fix generating lookup for repeated.items.any.in

[stitchcula]

Fix generating lookup for:

message RepeatedAnyIn { 
    repeated google.protobuf.Any val = 1 [(validate.rules).repeated.items.any = {in: [
        "type.googleapis.com/google.protobuf.Duration"
    ]}]; 
}

message RepeatedAnyNotIn { 
    repeated google.protobuf.Any val = 1 [(validate.rules).repeated.items.any = {not_in: [
        "type.googleapis.com/google.protobuf.Timestamp"
    ]}]; 
}

[elliotmjackson]

thanks for your contribution @stitchcula