Double quotes on selectors

Selector queries need double quotes on column names
##### Relevant URLs
https://docs.influxdata.com/influxdb/cloud-iox/reference/sql/functions/selectors/#selector-functions-in-use
From:
```
SELECT
selector_first(temp, time)['time'] AS time,
selector_first(temp, time)['value'] AS temp,
room
FROM home
GROUP BY room
```

To

```
SELECT
selector_first("temp", "time")['time'] AS time,
selector_first("temp", "time")['value'] AS temp,
room
FROM home
GROUP BY room
```
Thank you!

Open the selector functions example at the linked InfluxDB documentation URL and compare the current query with the requested version. Update the selector column references to use double quotes, then verify the rendered example and SQL syntax on that page.

Written by the indexing model from the issue text.