Documentation: Expired feedback form

[daira]

Split from #6742 by @metalworker2 :

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I found these issues in the docs when I was following the instructions for installing on Debian/Ubuntu officially supported platform:

https://zcash.readthedocs.io/en/latest/rtd_pages/install_debian_bin_packages.html

Expired feedback form

At the top of the documentation page is a link that says "Leave feedback". The link leads a page that says:

Sorry, the file that you've requested has been deleted.

https://docs.google.com/forms/d/e/1FAIpQLSf-QRiMN2IwoPKyei5N3vjfYTiay4a_1lXfW4rcbQZBnZ2tmg/viewform?usp=send_form