Upgrade spf13/cobra to v1.1.1 to fix zsh completion issue

[ysam12345]

Description

• Upgrade spf13/cobra from v1.0.0 to v1.1.1 to fix zsh autocomplete error when calling eksctl create nodegroup - invalid option definition #2747
• Modify test case of CLI because after v1.1.0 spf13/cobra change some error output from stdOut to stdErr. See Fix stderr printing functions spf13/cobra#894

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Added labels for change area (e.g. area/nodegroup), target version (e.g. version/0.12.0) and kind (e.g. kind/improvement)
• Make sure the title of the PR is a good description that can go into the release notes

[michaelbeaumont]

This is good to go in, we should refactor these tests (see #2747 (comment))

[michaelbeaumont]

Thanks @ysam12345 !

[ysam12345]

@michaelbeaumont I’m happy to help!