Merge pull request #62443 from WanLinghao/crd_column_fix

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 get CRD resources with --server-print=true column name error

**What this PR does / why we need it**:
Here's a bunch of kubectl get command execution and their outputs.
my-crd is the user-define CRD resource.
1. 
```
kubectl get pod --all-namespaces --server-print=true

NAMESPACE   NAME    READY   STATUS  RESTARTS   AGE
test-ns    test-pod  1/1    running     1      15m

```
2. 
```
kubectl get my-crd --all-namespaces --server-print=false

NAMESPACE   NAME      AGE
test-ns    test-crd    21m
```

3.
```
kubectl get my-crd --all-namespaces --server-print=true

NAMESPACE   NAME        CREATED AT
test-ns    test-crd         21m
```

Here's the problem
1. Example 3 isn't consistent with example 1 and 2
2. CREATED AT 21m doesn't make sense

This patch fix this.




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

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

staging/src/k8s.io/apiextensions-apiserver/pkg/registry/customresource/tableconvertor/tableconvertor.go

@@ -42,7 +42,7 @@ var swaggerMetadataDescriptions = metav1.ObjectMeta{}.SwaggerDoc()
 func New(extensions spec.Extensions) (rest.TableConvertor, error) {
 	headers := []metav1beta1.TableColumnDefinition{
 		{Name: "Name", Type: "string", Format: "name", Description: swaggerMetadataDescriptions["name"]},
-		{Name: "Created At", Type: "date", Description: swaggerMetadataDescriptions["creationTimestamp"]},
+		{Name: "Age", Type: "date", Description: swaggerMetadataDescriptions["creationTimestamp"]},
 	}
 	c := &convertor{
 		headers: headers,