Update AWS Athena connection string examples

The connection string examples for AWS athena aren't clear. We need to update them to align with connections strings outlined here: https://docs.aws.amazon.com/athena/latest/ug/querying.html#query-results-specify-location-previous-defaults.

##### Relevant URLs
- https://docs.influxdata.com/flux/v0.x/query-data/sql/athena/
- https://docs.influxdata.com/flux/v0.x/stdlib/sql/from/
- https://github.com/influxdata/flux/blob/master/stdlib/sql/awsathena.go
- https://github.com/influxdata/flux/blob/master/stdlib/sql/sql.flux

Open the AWS Athena connection examples at https://docs.influxdata.com/flux/v0.x/query-data/sql/athena/ and compare them with the AWS query-results documentation linked in the issue. Review the Flux SQL Athena references for context, then update the examples so their connection strings align with AWS guidance. Done means the documented examples use the current connection-string format.

Written by the indexing model from the issue text.