Documentation on `ingress.kubernetes.io/force-ssl-redirect` is outdated

[jwnx]

What steps did you take and what happened: Since https://github.com/projectcontour/contour/pull/252, Contour leverages HttpsRedirect instead of RequireTls to enforce force-ssl-redirect. All documentation versions are affected.

What did you expect to happen: The documentation would describe the correct behavior.

Anything else you would like to add: The ingress.kubernetes.io/force-ssl-redirect annotation was introduced by https://github.com/projectcontour/contour/pull/149 in Jan, 2018. Its documentation was first written in https://github.com/projectcontour/contour/commit/9e166f39d86069cdd1ae8cab2546aa0f461d1401 on Fev 6th, 2018 and the https://github.com/projectcontour/contour/pull/252 fix was merged on Feb 26th, 2018, but the documentation wasn't updated since then.

Environment: N/A

[github-actions[bot]]

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