Remove read permission for others on sensible log files

[yubiuser]

• What does this PR aim to accomplish?:

Removed the read permission for others for certain files:

1. /var/log/pihole/pihole.log(dnsmasq log file)
2. the debug log

Both files can contain highly sensible data and should not be readable by everyone.

P.S. pihole -t needs sudo powers now, tailing via the web interface still works.

• What documentation changes (if any) are needed to support this PR?:

Make change visible in the release notes

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2. I have commented my proposed changes within the code and I have tested my changes.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

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[dschaper]

Could be 660 but comme ci, comme ca...

[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-v5-16-web-v5-13-and-core-v5-11-1-released/56384/1

[pralor-bot]

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

https://discourse.pi-hole.net/t/html-permissions/58272/16