Firefox ignores the line-height because it declares line-height with `normal !important` in one of it's browser stylesheets. This can result in missing dots above umlauts.
props helen, lessbloat.
fixes#23189
git-svn-id: http://core.svn.wordpress.org/trunk@23976 1a063a9b-81f0-0310-95a4-ce76da25c4cd