fix(style): 删除全局 el-dropdown-menu padding 4px 规则

- global.scss 移除 .el-dropdown__popper .el-dropdown-menu { padding: 4px 0 !important; }
- gerp-user-dropdown 自带 padding: 0 生效，用户下拉菜单无首尾空隙

src/styles/global.scss

@@ -233,9 +233,6 @@ html.dark {
   list-style: none;
 }
 
-.el-dropdown__popper .el-dropdown-menu {
-  padding: 4px 0 !important;
-}
 
 .el-cascader__dropdown .el-scrollbar__wrap {
   padding-top: 0 !important;