Fix line-height for Button blocks in Twenty Nineteen

[sabernhardt]

Moves line-height to Buttons container and removes the duplicate outline

Trac 58443

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[github-actions]

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Props sabernhardt, audrasjb, poena.

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[github-actions]

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[audrasjb]

I restarted the jobs, since the Theme ZIP Build test for Twenty Nineteen was failing

[audrasjb]

This test is still failing

[carolinan]

Do I understand correctly from the error report that the rtl css files need to be re-built from the scss files and added to the PR?

[sabernhardt]

Yes, the RTL stylesheet needed to be built.

[SergeyBiryukov]

Thanks for the PR! Merged in r57599.