Revert "Add newsletter signup to main page"
Revert "Add newsletter signup to main page"

This reverts commit 3c45fa662613286af92176fc584fcaf4185a8167.

Removing because we're moving to Typeform from Google forms because
Google forms are ugly and typeforms are nicely designed.

openinfrastructure/openinfrastructure.github.io,openinfrastructure/openinfrastructure.github.io,openinfrastructure/openinfrastructure.github.io,openinfrastructure/openinfrastructure.github.io