修复单词错误 (#3675)

修复单词错误

Author: neilguangzhou

src/instance/internal/init.js

@@ -68,7 +68,7 @@ export default function (Vue) {
 
     // fragment:
     // if this instance is compiled inside a Fragment, it
-    // needs to reigster itself as a child of that fragment
+    // needs to register itself as a child of that fragment
     // for attach/detach to work properly.
     this._frag = options._frag
     if (this._frag) {