fix: use darwin instead of mac for kubernetes.io/os label

[tuananh]

Signed-off-by: Tuan Anh Tran [email protected]

1. Issue, if available:

2. Description of changes:

i thought kubernetes.io/os values is from runtime.GOOS as defined by Go. the list is here
https://github.com/golang/go/blob/a19e72cb89fd33e5bf1474887e267806f65b7a40/src/go/build/syslist.go#L10

const goosList = "aix android darwin dragonfly freebsd hurd illumos ios js linux nacl netbsd openbsd plan9 solaris windows zos "

in there, macOS is darwin instead of mac.

https://kubernetes.io/docs/reference/labels-annotations-taints/#kubernetes-io-os

3. Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: link to issue
• No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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