Merge pull request kubernetes#53575 from dahefanteng/master

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>.

remove repeated type conversion

**What this PR does / why we need it**:
remove repeated type conversion(convert String to Feature)
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
we just need make this conversion once.
**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

staging/src/k8s.io/apiserver/pkg/util/feature/feature_gate.go

@@ -157,7 +157,7 @@ func (f *featureGate) Set(value string) error {
 		}
 		arr := strings.SplitN(s, "=", 2)
 		k := Feature(strings.TrimSpace(arr[0]))
-		_, ok := known[Feature(k)]
+		_, ok := known[k]
 		if !ok {
 			return fmt.Errorf("unrecognized key: %s", k)
 		}