Bundled Themes: Twenty Sixteen table border extends beyond table.

Fixes issues where tables created by the table block have an extra border on the left side which extends below the table.

Props gsmumbo, mukesh27, JavierCasares.
Fixes #50180.
Built from https://develop.svn.wordpress.org/trunk@48074


git-svn-id: https://core.svn.wordpress.org/trunk@47841 1a063a9b-81f0-0310-95a4-ce76da25c4cd