remove import doc comments

The "// import <path>" comment has been superseded by Go modules.
We don't have to remove them, but doing so has some advantages:

- They are used inconsistently, which is confusing.
- We can then also remove the (currently broken) hack/update-vanity-imports.sh.
- Last but not least, it would be a first step towards avoiding the k8s.io domain.

This commit was generated with
   sed -i -e 's;^package \(.*\) // import.*;package \1;' $(git grep -l '^package.*// import' | grep -v 'vendor/')

Everything was included, except for
   package labels // import k8s.io/kubernetes/pkg/util/labels
because that package is marked as "read-only".

pkg/controller/namespace/config/doc.go

@@ -16,4 +16,4 @@ limitations under the License.
 
 // +k8s:deepcopy-gen=package
 
-package config // import "k8s.io/kubernetes/pkg/controller/namespace/config"
+package config

pkg/controller/namespace/config/v1alpha1/doc.go

@@ -18,4 +18,4 @@ limitations under the License.
 // +k8s:conversion-gen=k8s.io/kubernetes/pkg/controller/namespace/config
 // +k8s:conversion-gen-external-types=k8s.io/kube-controller-manager/config/v1alpha1
 
-package v1alpha1 // import "k8s.io/kubernetes/pkg/controller/namespace/config/v1alpha1"
+package v1alpha1

pkg/controller/namespace/doc.go

@@ -15,4 +15,4 @@ limitations under the License.
 */
 
 // Package namespace contains a controller that handles namespace lifecycle
-package namespace // import "k8s.io/kubernetes/pkg/controller/namespace"
+package namespace