Kibana version: 8.0.0

Elasticsearch version: 8.0.0

Server OS version: Linux

Browser version: Chrome

Browser OS version: Windows

Original install method (e.g. download page, yum, from source, etc.):
source

Describe the bug:
I create a saved search in Discover, and it's loading fine. But when I got to Advanced Settings and change the dateFormat:tz setting from Browser (default) to MST, Discover stops being able to show the search.

Steps to reproduce:

1. Use test data

PUT my_index
{
  "mappings": {
      "properties": {
        "date": {
          "type": "date" 
        },
        "name": {
          "type": "keyword" 
        }
      }
    }
}

PUT my_index/_doc/1
{
  "date": "2019-01-01",
  "name": "Raiden"
} 

PUT my_index/_doc/2
{
  "date": 1546300800001,
  "name": "Sub-Zero"
} 

PUT my_index/_doc/3
{
  "date": "2019-01-01T12:10:30Z",
  "name": "Scorpion"
} 

2. Create a basic index pattern
3. Create a saved search in Discover based on the index pattern
4. Change dateFormat:tz setting from default in Advanced Settings to MST
5. Reload the saved search

Expected behavior:
Discover shows the data with the date values formatted in the set time zone

Screenshots (if relevant):

Errors in browser console (if relevant):

{"statusCode":400,"error":"Bad Request","message":"[x_content_parse_exception] [1:172] [date_histogram] failed to parse field [time_zone]","attributes":{"error":{"root_cause":[{"type":"x_content_parse_exception","reason":"[1:172] [date_histogram] failed to parse field [time_zone]"}],"type":"x_content_parse_exception","reason":"[1:172] [date_histogram] failed to parse field [time_zone]","caused_by":{"type":"zone_rules_exception","reason":"Unknown time-zone ID: MST"}}}}

Provide logs and/or server output (if relevant):

Any additional context: