Twenty Seventeen: Ensure edit button label displays properly in other languages

This bug occurred in any language where text wraps character-by-character, since those languages don't delimit words with spaces. In Japanese, Chinese and Korean, etc., it was possible for the label to be displayed vertically.

Props tg29359, afercia, odysseygate.

Fixes #38876.

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git-svn-id: https://core.svn.wordpress.org/trunk@39281 1a063a9b-81f0-0310-95a4-ce76da25c4cd