docs: add instructions to check license header in "How to verify a release"

[kevinjqliu]

Which issue does this PR close?

• Closes docs: add pyiceberg-core to "how to verify a release" #1660

What changes are included in this PR?

We already use apache/skywalking-eyes in the release script and in CI

Preview:

Are these changes tested?

Verified with https://downloads.apache.org/iceberg/apache-iceberg-rust-0.6.0/

➜  apache-iceberg-rust-0.6.0-src docker run -it --rm -v $(pwd):/github/workspace apache/skywalking-eyes header check
INFO Loading configuration from file: .licenserc.yaml 
INFO Totally checked 312 files, valid: 262, invalid: 0, ignored: 50, fixed: 0 

[liurenjie1024]

Thanks @kevinjqliu for this fix!