Fix #3055

[luochen1990]

Accroding to README.md:

Note: Adding new regexp and keyword rules is discouraged because it is easy to use them incorrectly, and proxy software cannot efficiently match these types of rules.

[Meo597]

Unless absolutely necessary, avoid using regular expressions.
They are not only prone to errors (this is an example).
But also have terrible performance. Domain rules don't actually have such strict requirements.
domain and keyword are both fast