Update calypso-build to 5.1

[glendaviesnz]

Updates calypso build to 5.1 which introduces the nullish coalescing operator and optional chaining
plugins. Both of these are now being used in the calypso code base so would be good for them to be an option in the jetpack javascript modules.

Feel free to just close this if there are reasons why we wouldn't want to upgrade the calypso build module at this point.

Changes proposed in this Pull Request:

• Updates @automattic/calypso-build version in package.json

Testing instructions:

Not sure on the best way to test this - ran all of the build scripts in package.json and nothing seems to be broken.

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello glendaviesnz! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer, review, and approve D37503-code before merging this PR. Thank you!

[jetpackbot]

	Warnings
⚠️	The PR is missing at least one [Status] label. Suggestions: [Status] In Progress, [Status] Needs Review
⚠️	"Proposed changelog entry" is missing for this PR. Please include any meaningful changes

This is an automated check which relies on PULL_REQUEST_TEMPLATE. We encourage you to follow that template as it helps Jetpack maintainers do their job. If you think 'Testing instructions' or 'Proposed changelog entry' are not needed for your PR - please explain why you think so. Thanks for cooperation 🤖

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[glendaviesnz]

Closing as a duplicate of #14194