fix: correct preface en version sidebar

docs/index.html

@@ -214,7 +214,6 @@
             alias: {
                 // 英文路径映射
                 '/en/README.md': '/README_EN.md',
-                '/en/Preface.md': '/Preface.md',
                 '/en/_sidebar.md': '/_sidebar_en.md',
                 '/en/chapter(\\d+)/Chapter(.*)': '/chapter$1/Chapter$2',