Twenty Fifteen: clean up of `twentyfifteen_color_scheme_css_template()` in customizer.php. Props iamtakashi. Fixes #30601.
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Admin toolbar: remove unneeded overrides of `z-index` and `left` on screens narrower than 782px. Props avryl, babbardel. Fixes #29867.
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WP_HTTP: Revert r30491 which updated the bundled root certificates. There's a report that this is breaking under certain PHP/OpenSSL versions (which we've encountered before), and we're safer with a slighty out of date CA bundle than breaking HTTPS communication on affected sites.
See #30434

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git-svn-id: http://core.svn.wordpress.org/trunk@30755 1a063a9b-81f0-0310-95a4-ce76da25c4cd