chore(data bridge): comment example config

Signed-off-by: zhanghongtong <rory-z@outlook.com>

apps/emqx_data_bridge/etc/emqx_data_bridge.conf

@@ -3,28 +3,28 @@
 ##--------------------------------------------------------------------
 
 emqx_data_bridge.bridges: [
-    {name: "mysql-abc"
-     type: mysql
-     config: {
-        server: "127.0.0.1:3306"
-        database: mqtt
-        pool_size: 1
-        user: root
-        password: public
-        auto_reconnect: true
-        ssl: false
-     }
-    },
-    {name: "mysql-def"
-     type: mysql
-     config: {
-        server: "127.0.0.1:3306"
-        database: mqtt
-        pool_size: 1
-        user: root
-        password: public
-        auto_reconnect: true
-        ssl: false
-     }
-    }
+#    {name: "mysql-abc"
+#     type: mysql
+#     config: {
+#        server: "127.0.0.1:3306"
+#        database: mqtt
+#        pool_size: 1
+#        user: root
+#        password: public
+#        auto_reconnect: true
+#        ssl: false
+#     }
+#    },
+#    {name: "mysql-def"
+#     type: mysql
+#     config: {
+#        server: "127.0.0.1:3306"
+#        database: mqtt
+#        pool_size: 1
+#        user: root
+#        password: public
+#        auto_reconnect: true
+#        ssl: false
+#     }
+#    }
 ]