Change database permissions to -rw-r----- (640)

[DL6ER]

What does this implement/fix?

See title. Fixes pi-hole/pi-hole#5569

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Related issue or feature (if applicable): pi-hole/pi-hole#5569

Pull request in docs with documentation (if applicable): N/A

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[yubiuser]

Needs an addition also here:
https://github.com/pi-hole/pi-hole/blob/200a82acfb268630e82d40b2f5ff2f8149d8cc2e/advanced/Templates/pihole-FTL-prestart.sh#L17

[DL6ER]

@yubiuser The permissions are changed by FTL after this other place so it's not reversing them really