Disable redundant/superfluous CI jobs

[regexident]

There is basically no way for cargo clippy to succeed if cargo check doesn't, so the latter is redundant.

Likewise we shouldn't need to run cargo minimal-versions check + cargo minimal-versions build + cargo minimal-versions test. All we should need is cargo minimal-versions check --tests, since check is a subset of build, which in turn is practically a subset of test, which we're already running separately. We're thus only interested in whether or not the code compiles, for which check --tests is the quickest.