Cannot set the Window Period when creating a check in the Alerts page

__Steps to reproduce:__
List the minimal actions needed to reproduce the behavior.

1. Start influxdb, create bucket, add measurements with numerical data fields
2. Create a check in the alerts page on one of the numerical data fields

__Expected behavior:__

On the define query page, I expect to be able to set the 'WINDOW PERIOD' field for the aggregate function, as is possible when querying data on the 'Expore Data' page.

__Actual behavior:__

I cannot set the 'WINDOW PERIOD' at all. It is stuck on it's auto value and greyed out

__Environment info:__

Linux 5.8.0-34-generic x86_64 (docker image)
**Host machine:** Linux 5.8.0-34-generic x86_64 (VM)
InfluxDB 2.0.3 (git: fe04d346df) build_date: 2020-12-15T01:00:16Z

Reproduce the issue through the Alerts page by creating a check with numerical data, then inspect the Define Query page and compare its aggregate-function controls with the Explore Data page. Done means the WINDOW PERIOD field can be set instead of remaining greyed out at its automatic value.

Written by the indexing model from the issue text.