[Log UI] Move UI warning in the log threshold rule type closer to the group by section

[mgiota]

While testing #104354 on cloud 7.14 the UI warning appeared
but I would expect it to appear above the Query A and Query B sections. I had to scroll down to realize that the warning was indeed there.

Acceptance criteria
Consider if it makes sense to move it closer to the Group by section

How to test
Create a log threshold rule type and set a group by with an unoptimised comparator (anything that can evaluate 0 as a threshold). For more details have a look at the the PR that introduced the UI warning #102650

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)

[elasticmachine]

Pinging @elastic/actionable-observability (Team: Actionable Observability)

[maryam-saeidi]

Will be fixed in the new combined threshold rule: https://github.com/elastic/actionable-observability/issues/36