CI: some CI workers are slow, so use bigger margin for test duration

[FSchumacher]

Description

Set a bigger margin for the scheduler to end in one flaky test

Motivation and Context

Some CI workers seem to be slow and we get less value of a flaky test. We already gave one second margin. The slow workers often used 400 ms more, so use two seconds margin, to be on the safe(r) side.

How Has This Been Tested?

Let the CI builds decide :)

Screenshots (if appropriate):

Types of changes

• CI fix (hopefully)

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.