error message is too generic when creating a silence with end time before start

Description of problem:

login administrator console UI, create silence for Watchdog alert, set "Until" time to a past time, click "Silence" button would see 

An error occurred
Bad Request

the error message is not clear, add the response to error message is more clear

"Failed to create silence: start time must be before end time"

Version-Release number of selected component (if applicable):

4.12.0-0.nightly-2022-11-08-002816

How reproducible:

always

Steps to Reproduce:

1. create silence for Watchdog alert, set "Until" time to a past time, click "Silence" button
2.
3.

Actual results:

error message is not clear

Expected results:

add the response to error message is more clear

Additional info: