[7.x](backport #28364) [Metricbeat] gcp: fix integration tests

[mergify]

This is an automatic backport of pull request #28364 done by Mergify.
Cherry-pick of e8066e9 has failed:

On branch mergify/bp/7.x/pr-28364
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit e8066e9fb6.
  (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)

Changes to be committed:
	modified:   CHANGELOG-developer.next.asciidoc
	modified:   dev-tools/mage/common.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   x-pack/metricbeat/module/gcp/DEVELOPMENT.md
	both modified:   x-pack/metricbeat/module/gcp/billing/billing_integration_test.go

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

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Pinging @elastic/integrations (Team:Integrations)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2021-10-14T07:38:44.549+0000

• Duration: 165 min 38 sec

• Commit: c611e59

Test stats 🧪

Test	Results
Failed	0
Passed	54141
Skipped	5271
Total	59412

💚 Flaky test report

Tests succeeded.

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[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/7.x/pr-28364 upstream/mergify/bp/7.x/pr-28364
git merge upstream/7.x
git push upstream mergify/bp/7.x/pr-28364