matrix_sync: 修改插件介绍信息的路径 (#444)

Change introduction path

plugins/matrix_sync/plugin_info.json

@@ -11,7 +11,7 @@
     "related_path": ".",
     "labels": ["tool", "information"],
     "introduction": {
-        "en_us": "doc/introduction.md",
-        "zh_cn": "doc/introduction-zh_cn.md"
+        "en_us": "descriptions/en_us.md",
+        "zh_cn": "descriptions/zh_cn.md"
     }
 }