[8.19](backport #45127) [oteltest][fbreceiver] Fix flaky test

[mergify]

In our otelbeat's test cases, we use require.EventuallyWithT to test certain conditions which are satisfied after some time. For eg. status reporter.
While asserting conditions, we should pass *assert.CollectT variable and not the parent testing.T. Passing the parent variable will lead to instant failure because of the underlying logic of EventuallyWithT.

Closes #45057

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This is an automatic backport of pull request #45127 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of dd5cbac has failed:

On branch mergify/bp/8.19/pr-45127
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit dd5cbacf4.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   libbeat/otelbeat/oteltest/oteltest.go
	both modified:   x-pack/filebeat/fbreceiver/receiver_test.go

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[VihasMakwana]

Fixed via #45045. No backport needed