[7.17](backport #29710) use main default branch

[mergify]

This is an automatic backport of pull request #29710 done by Mergify.
Cherry-pick of 2379370 has failed:

On branch mergify/bp/7.17/pr-29710
Your branch is up to date with 'origin/7.17'.

You are currently cherry-picking commit 237937085a.
  (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:   .ci/apm-beats-update.groovy
	modified:   .ci/beats-tester.groovy
	modified:   .ci/jobs/beats-schedule-weekly.yml
	modified:   .ci/packer_cache.sh
	modified:   CHANGELOG-developer.next.asciidoc
	modified:   CHANGELOG.next.asciidoc
	modified:   Jenkinsfile
	modified:   dev-tools/cherrypick_pr
	modified:   dev-tools/merge_pr
	modified:   dev-tools/open_pr
	modified:   docs/devguide/contributing.asciidoc
	modified:   docs/devguide/create-metricset.asciidoc
	modified:   docs/devguide/metricset-details.asciidoc
	modified:   docs/devguide/migrate-dashboards.asciidoc
	modified:   libbeat/docs/communitybeats.asciidoc
	modified:   libbeat/docs/upgrading.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   .ci/beats-tester-bc.groovy
	deleted by us:   .ci/build-docker-images.groovy
	deleted by us:   .ci/jobs/apm-beats-update.yml
	deleted by us:   .ci/jobs/beats-schedule-daily.yml
	deleted by us:   .ci/jobs/beats-test-infra.yml
	deleted by us:   .ci/jobs/beats-tester-bc.yml
	both modified:   .ci/jobs/beats-tester.yml
	deleted by us:   .ci/jobs/beats.yml
	deleted by us:   .ci/jobs/build-it-docker-images.yml
	deleted by us:   .ci/jobs/packaging.yml
	deleted by us:   .ci/schedule-daily.groovy
	both modified:   .ci/schedule-weekly.groovy
	both modified:   .mergify.yml
	both modified:   CHANGELOG-developer.asciidoc
	both modified:   README.md
	deleted by us:   filebeat/_meta/test/docs/testing.md
	both modified:   x-pack/elastic-agent/README.md

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

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[botelastic]

This pull request doesn't have a Team:<team> label.

[elasticmachine]

❕ Build Aborted

Either there was a build timeout or someone aborted the build.

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Reason: null

• Start Time: 2022-02-03T10:06:50.189+0000

• Duration: 364 min 54 sec

• Commit: 51c9d52

Test stats 🧪

Test	Results
Failed	0
Passed	21037
Skipped	1539
Total	22576

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request has not been merged yet. Could you please review and merge it @v1v? 🙏

[v1v]

Not needed