Automatic merge from submit-queue

Fix Content-Type error of apis

**What this PR does / why we need it**:
Response's Content-type of `/apis` is `text/plain`, not `application/json`.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #44646 

**Special notes for your reviewer**:
We could use `responsewriters.WriteObjectNegotiated()` to write Content-type correctly.

**Release note**:

```release-note
```