Automatic merge from submit-queue (batch tested with PRs 59965, 59115, 63076, 63059). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

fix help message of kubeconfig-dir option(kubeadm alpha phase kubeconfig all)

**What this PR does / why we need it**:
This patch will fix wrong help message.

The command is kubeadm alpha phase kubeconfig [command]
The help message is for --kubeconfig-dir option.

kubeconfig-dir is not port.(It is directory)
So, I fixed the message.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

 `NONE`

/sig cluster-lifecycle