Fix CalendarInterval year alias

[esdrasbrz]

This PR fixes the AggregationsCalendarInterval type with 1y instead of 1Y. ElasticSearch 8.6 returns the following error when 1Y is used:

{
  "error": {
    "root_cause": [
      {
        "type": "x_content_parse_exception",
        "reason": "[41:30] [date_histogram] failed to parse field [calendar_interval]"
      }
    ],
    "type": "x_content_parse_exception",
    "reason": "[41:30] [date_histogram] failed to parse field [calendar_interval]",
    "caused_by": {
      "type": "illegal_argument_exception",
      "reason": "The supplied interval [1Y] could not be parsed as a calendar interval."
    }
  },
  "status": 400
}

Also, from the docs, the correct interval is 1y

Closes #2627

[esdrasbrz]

I'm not sure about the backports. It seems it needs backports as the API is only partially usable, but I can't change the PR labels.
LMK if there's something else I need to do.

[pquentin]

Great catch, thank you! And sorry for being so terribly late.