Increase wait time for slow ConfigurationManagementGraphServerTest

[FlorianHockmann]

The test has been failing quite often lately, probably simply because it didn't wait long enough for the new graph to be created, at least for slow hardware like we have with GH Actions.

I executed the test at least 10 times with this change in GH Actions and it didn't fail a single time so I guess that this increased timeout is enough.

Fixes #3849

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[porunov]

LGTM. Thank you @FlorianHockmann !
I was tired restarting this test 2-3 times for each PR 😅
I'm not sure, but it seems VMs in GitHub Actions just got weaker later (not 100% sure here). So, this could be the reason why this test started to fail more often than usually.

BTW. Another failing test in this PR isn't related to your changes. It's another flaky test described in #3841

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