[Function] Optimise an error when function deletion is failed

[rokatyy]

Currently, the error string can be too long, so I have removed the additional string about failure for every Nuclio function. There will still be a message indicating that the deletion failed, including the MLRun function name.

So, instead of this

Failed to delete function func-nuclio. Errors: Failed to delete nuclio function run-nuclio-hello-world-func-nuclio: 412, message='Precondition Failed', url=URL('http://nuclio-dashboard.default-tenant.svc.cluster.local:8070/api/functions/'): : Function is "

we will have:

Failed to delete function func-nuclio. Errors: Function is used by api gateways"

Jira - https://iguazio.atlassian.net/browse/ML-6552

[TomerShor]

@rokatyy can you updated the description with the new error after your latest change? I'd like to see how it look

[rokatyy]

@TomerShor updated