Language switcher no longer works without JavaScript

[alexgibson]

This may well be an intended change reading #5581, but I'm filing this as not 100% sure.

STR:

Using any browser with JS disabled, or a legacy browser such as IE8 (where we don't serve JS):

1.) Visit https://www.mozilla.org/en-US/
2.) Scroll down to the language switcher in the footer and choose "Francais" from the list (as an example).
3.) Hit the "Go" button to submit the form.

Expected results:

Page should redirect to https://www.mozilla.org/fr/

Actual results:

Page redirects to https://www.mozilla.org/en-US/?lang=fr (still English)

If we no longer want to support the language switcher without JavaSctipt that's OK by me, but we should probably then hide it by default, rather than leave it in a broken state.

[michaelmccombie]

Once we have the language selector page #5827 built out and added to the new footer mozilla/protocol#184 we will be able to provide that same functionality to those who have javascript disabled.

[conradylx]

I think this issue is already fixed.

[robhudson]

Tested this today and it is still an issue.

[stevejalim]

FYI i'm going to fold this work into my i18n-refactor work for #14256 - thanks for the contribution @Ingi-Hong