Corrected the example of the managed CSI plugin.

Review: https://reviews.apache.org/r/72846
diff --git a/docs/configuration/agent.md b/docs/configuration/agent.md
index 4899202..a8286d1 100644
--- a/docs/configuration/agent.md
+++ b/docs/configuration/agent.md
@@ -1528,16 +1528,10 @@
   "containers": [
     {
       "services": [
-        "CONTROLLER_SERVICE",
         "NODE_SERVICE"
       ],
       "command": {
-        "shell": false,
-        "value": "managed-plugin",
-        "arguments": [
-          "managed-plugin",
-          "--endpoint=$(CSI_ENDPOINT)"
-        ]
+        "value": "<path-to-managed-plugin> --endpoint=$CSI_ENDPOINT"
       },
       "resources": [
         {"name": "cpus", "type": "SCALAR", "scalar": {"value": 0.1}},
diff --git a/src/slave/flags.cpp b/src/slave/flags.cpp
index 878788c..e66b464 100644
--- a/src/slave/flags.cpp
+++ b/src/slave/flags.cpp
@@ -129,16 +129,10 @@
       "  \"containers\": [\n"
       "    {\n"
       "      \"services\": [\n"
-      "        \"CONTROLLER_SERVICE\",\n"
       "        \"NODE_SERVICE\"\n"
       "      ],\n"
       "      \"command\": {\n"
-      "        \"shell\": false,\n"
-      "        \"value\": \"managed-plugin\",\n"
-      "        \"arguments\": [\n"
-      "          \"managed-plugin\",\n"
-      "          \"--endpoint=$(CSI_ENDPOINT)\"\n"
-      "        ]\n"
+      "        \"value\": \"<path-to-managed-plugin> --endpoint=$CSI_ENDPOINT\"\n"
       "      },\n"
       "      \"resources\": [\n"
       "        {\"name\": \"cpus\", \"type\": \"SCALAR\", \"scalar\": {\"value\": 0.1}},\n" // NOLINT(whitespace/line_length)