Fix typo in comment for func IsReachable

Signed-off-by: Guangwen Feng <fenggw-fnst@cn.fujitsu.com>

pkg/kube/fake/printer.go

@@ -33,7 +33,7 @@ type PrintingKubeClient struct {
 	Out io.Writer
 }
 
-// isReachable checks if the cluster is reachable
+// IsReachable checks if the cluster is reachable
 func (p *PrintingKubeClient) IsReachable() error {
 	return nil
 }