Add katib-cli download command for Mac

[vinaykakade]

Added the missing command to download katib-cli on mac.

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[gaocegege]

Hi, is there any problem? I think the changes LGTM.

[googlebot]

CLAs look good, thanks!

[vinaykakade]

Closed this earlier to verify the CLA requirement. Signed the CLA.

I think this is now good to be merged.

[vinaykakade]

/assign @YujiOshima @gaocegege

[YujiOshima]

/ok-to-test

[YujiOshima]

/lgtm
@vinaykakade Thanks!

[YujiOshima]

/retest

[YujiOshima]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: YujiOshima

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