[Docs] Include index param in geo_point docs

[a-k-g]

Based on local testing in docker it seems that geo_point type fields actually support the index param. Docs don't seem to mention that currently.

Tested by creating an index with the following mapping on 6.8.16:

{
    "mappings": {
        "_doc": {
            "properties": {
                "fieldValue": {
                    "type": "geo_point",
                    "index": "false"
                }
            }
        }
    }
}

Also tested on 7.13.4 without nesting inside the _doc type.

• Have you signed the contributor license agreement? Yes
• Have you followed the contributor guidelines? Yes

Would be nice to port this back to previous versions too.

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)

[jrodewig]

@elasticmachine ok to test

[jrodewig]

LGTM. Thanks @a-k-g!

[a-k-g]

Great, thanks! Is there any action required to also backport this?

[jrodewig]

Is there any action required to also backport this?

I'll merge and backport this once our CI tests pass. Per our backporting policy, I'll backport to our currently maintained versions: 7.x, 7.14, 7.13, and 6.8.