ci: tweak minimum supported Rust handling
ci: tweak minimum supported Rust handling

lazy_static 1.2 bumped its MSRV to Rust 1.24.1, so we rollback to using
lazy_static 1.1 when testing on Rust versions older than 1.24.1.

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