Deprecation warnings from xml_builder

[hexedpackets]

Using xml_builder > 2.0.0 with ex_aws_route53 causes the following warning to be printed to stderr:

warning: doc/1 is deprecated. Use document/1 with generate/1 instead.
  (xml_builder 2.1.4) lib/xml_builder.ex:62: XmlBuilder.doc/1
  (ex_aws_route53 2.0.2) lib/ex_aws/route53.ex:101: ExAws.Route53.change_record_sets/2
  (atuin 0.1.0) lib/atuin/trigger/webhook/dns.ex:23: Atuin.Trigger.Webhook.DNS.route53_update/3
  (stdlib 3.14.1) erl_eval.erl:680: :erl_eval.do_apply/6
  (elixir 1.12.2) src/elixir.erl:280: :elixir.recur_eval/3
  (elixir 1.12.2) src/elixir.erl:265: :elixir.eval_forms/3

This happens at runtime on every call with ex_aws_route53 (its an IO.warn call in the doc/1 function).

The deprecation warning was added in 2.1.0, so possible solutions would be to either set the dependency to < 2.1.0 or update the calling code and set the dependency to >= 2.1.0. Considering that 2.1.0 was released over 3 years ago I would guess that its pretty safe to set 2.1.0 as the lower bounds.