Exclude cherry-pick-stable script from crates.io package

[SwishSwushPow]

Description

While reviewing dependencies at my company I noticed that with libc 0.2.177 the cherry-pick-stable.sh script showed up in the package published to crates.io. I suspect that it is not required to be shipped and I open this PR to exclude it from the package. This makes code review for supply chain safety a bit easier because we don't have to review future changes to the script and not having a script in the published package is also a good thing. :)

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

Since this is targeting 0.2 I think the stable label is warrented? Sorry if I'm getting something wrong here. 😅

@rustbot label +stable-nominated

[rustbot]

⚠️ Warning ⚠️

• Pull requests are usually filed against the main branch for this repo, but this one is against libc-0.2. Please double check that you specified the right target!