Twenty Seventeen: Fix CSS specificity problem with CSS feature query for `object-fit`

Previously, the theme's CSS feature query for `object-fit` overrode styles it shouldn't have on interior pages.

This moves the feature query farther down in the stylesheet so it takes precedence in the cascade in supported browsers, and applies the appropriate selector for the interior pages. In browsers that don't support feature queries or `object-fit`, the fallback styles are still applied. The problem was that the rules had the same specificity, so this way, the cascade takes over properly. The transforms and position changes for fallbacks are still needed in browsers that don't support `object-fit` and feature queries.

Props peterwilsoncc, davidakennedy.

Fixes #39073.

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git-svn-id: https://core.svn.wordpress.org/trunk@39435 1a063a9b-81f0-0310-95a4-ce76da25c4cd