GoogleContainerTools/skaffold mainline branch is called 'main' other than 'master'

[kim-fitness]

GoogleContainerTools/skaffold mainline branch is called 'main' other than 'master'

Changes

docs/tutorial.md

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• [N/A] Docs included if any changes are user facing
• [N/A] Tests included if any functionality added or changed
• Follows the commit message standard
• Meets the Tekton contributor standards (including
  functionality, content, code)
• [N/A] Release notes block below has been filled in or deleted (only if no user facing changes)

Release Notes

[tekton-robot]

Hi @kim-fitness. Thanks for your PR.

I'm waiting for a tektoncd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kim-fitness]

/assign @dlorenc

[vdemeester]

/ok-to-test
/kind documentation
/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vdemeester

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[ghost]

/lgtm

/test pull-tekton-pipeline-alpha-integration-tests

/test pull-tekton-pipeline-integration-tests