调整正确的语言文字，用户名必须6-30个字符

Signed-off-by: 椒颜玉米粒 <1336749157@qq.com>

application/index/lang/zh-cn/user.php

@@ -23,7 +23,7 @@ return [
     'Email active successful'                    => '邮箱激活成功',
     'Username can not be empty'                  => '用户名不能为空',
     'Username must be 3 to 30 characters'        => '用户名必须3-30个字符',
-    'Username must be 6 to 30 characters'        => '用户名必须3-30个字符',
+    'Username must be 6 to 30 characters'        => '用户名必须6-30个字符',
     'Account must be 3 to 50 characters'         => '账户必须3-50个字符',
     'Password can not be empty'                  => '密码不能为空',
     'Password must be 6 to 30 characters'        => '密码必须6-30个字符',