fix: fix snprintf arg list.

[lI15SO0]

Origin snippet at c.json:300

 "snprintf": {
        "prefix": "snprintf",
        "body": ["snprintf(${1:buf}, ${2:max}, \"${3:%s}\\n\"$3);$0"],
        "description": "snprintf() snippet"
    },

When i use this snippet , it will fill like this.

Fix it by replace the second $3 to $4