Number of domains on adlist is total number not valid number

[yubiuser]

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What does this PR aim to accomplish?:

Only change wording. We report for every adlist the number of domains on that list. Previously, this number was name "valid domains", which is incorrect. Actually, we store the number of total domains of that list, not the number of valid domains (which can, obviously, be smaller)

https://github.com/pi-hole/pi-hole/blob/b5e0f142ccefe9b1b59b94d7e82d3052efbfdcd0/gravity.sh#L251

and

https://github.com/pi-hole/pi-hole/blob/b5e0f142ccefe9b1b59b94d7e82d3052efbfdcd0/gravity.sh#L520-L521

[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-v5-12-web-v5-9-and-core-v5-7-released/51795/1