Use simpler regex format for wildcards

[AzureMarker]

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What does this PR aim to accomplish?:
Use a simpler wildcard regex format proposed here

How does this PR accomplish the above?:
Use \.?domain\.com$ instead of ((^)|(\.))domain\.com$

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

See also pi-hole/pi-hole#2318

[pralor-bot]

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

https://discourse.pi-hole.net/t/sugestings-about-name-giving-lists/11216/4

[DL6ER]

This regex is equivalent. Although it should be identical, the number of parenthesized subexpressions is reduced (one instead of three) so it might actually slightly improve the speed of the regex validator.