Do not default true for unset variables DNS_FQDN_REQUIRED and DNS_BOGUS_PRIV

[yubiuser]

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What does this PR aim to accomplish?:

Do not default true for unset variables. When DNS_FQDN_REQUIRED and DNS_BOGUS_PRIV have not been set in setupVars.conf at all, the relevant checkboxes in the web GUI were checked anyway. We don't do that for other variables (e.g. DNSSEC) and I think we shouldn't do this. If something is not set at all, we can not pretend it would be true.

How does this PR accomplish the above?:

Change the default to false

What documentation changes (if any) are needed to support this PR?:
None.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-11-web-v5-8-and-core-v5-6-released/50566/1