📖 improve builder deprecation messages

[terinjokes]

It's convention in the Go community that a function's deprecation notice
is separated by a new paragraph from the function's documentation. Tools
like staticcheck determine if a function has been deprecated by checking
the beginning of new paragraphs.

This changelist modifies the deprecation notices in the builder package
to follow this convention, allowing linters like staticcheck,
gometalinter, and golangci-lint to warn users of the package.

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[DirectXMan12]

please sign the CLA, otherwise looks good. Thanks!

[terinjokes]

@DirectXMan12 Waiting on the 👍 for that. Will poke the bot after it gets resolved.

[DirectXMan12]

/lgtm
/approve

Thanks!

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: DirectXMan12, terinjokes

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