[zh] modify busybox to busybox:1.28 in dir examples

Signed-off-by: xin.li <xin.li@daocloud.io>

content/zh/examples/pods/security/hello-apparmor.yaml

@@ -9,5 +9,5 @@ metadata:
 spec:
   containers:
   - name: hello
-    image: busybox
+    image: busybox:1.28
     command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]

content/zh/examples/pods/security/security-context.yaml

@@ -12,7 +12,7 @@ spec:
     emptyDir: {}
   containers:
   - name: sec-ctx-demo
-    image: busybox
+    image: busybox:1.28
     command: [ "sh", "-c", "sleep 1h" ]
     volumeMounts:
     - name: sec-ctx-vol