Automatic merge from submit-queue. 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>.

kubectl: Remove swagger 1.2 entirely.

**What this PR does / why we need it**:
Remove dead code since nothing is using swagger 1.2 anymore. This doesn't change any feature, it's just removing unused code.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: Follow up on #44589

**Special notes for your reviewer**:

**Release note**:
```release-note
NONE
```