ci: remove minimal version check
ci: remove minimal version check

It's impossible to do this without the cooperation of maintainers from
other core crates, and some of them do not see the value in doing this.

rust-lang/regex,rust-lang/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang/regex,rust-lang/regex,rust-lang-nursery/regex,rust-lang/regex,rust-lang-nursery/regex