tb-manual: sidebar does not move to the other side when on ltr languages

When choosing Arabic in the tb-manual the website is mostly moved to ltr, but some things stay on the rtl position, like the sidebar and some parts of the footer (newsletter)

See https://lektor-staging.torproject.org/tor-browser-manual/staging/ar/ and compare it with https://lektor-staging.torproject.org/tor-browser-manual/staging/