Updated branch reference for the tutorial

[Nicwalle]

This pull request includes a minor change to the az acr task create command in the articles/container-registry/container-registry-tutorial-base-image-update.md file. The change modifies the --context argument to point to the master branch instead of the main branch in the acr-build-helloworld-node.git repository.

[prmerger-automator[bot]]

@Nicwalle : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[learn-build-service-prod[bot]]

Learn Build status updates of commit 1a8de08:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
articles/container-registry/container-registry-tutorial-base-image-update.md	:white_check_mark:Succeeded

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[Court72]

@tejaswikolli-web

Can you review the proposed changes?

When the changes are ready for publication, add a #sign-off comment to signal that the PR is ready for the review team to merge.

label:"aq-pr-triaged"

@MicrosoftDocs/public-repo-pr-review-team

[tejaswikolli-web]

sign-off

[Jak-MS]

Due to the upcoming Build conference, all merging and publishing is on hold until the morning of 5/21.

This PR is ready for merge on 5/21.

label: "event-triaged-to-10AM"

label: "missed-content-complete"