【代码修复】system：移除用户账号正则检验中长度限制

yudao-module-system/yudao-module-system-biz/src/main/java/cn/iocoder/yudao/module/system/controller/admin/user/vo/user/UserSaveReqVO.java

@@ -23,7 +23,7 @@ public class UserSaveReqVO {
 
     @Schema(description = "用户账号", requiredMode = Schema.RequiredMode.REQUIRED, example = "yudao")
     @NotBlank(message = "用户账号不能为空")
-    @Pattern(regexp = "^[a-zA-Z0-9]{4,30}$", message = "用户账号由 数字、字母 组成")
+    @Pattern(regexp = "^[a-zA-Z0-9]$", message = "用户账号由 数字、字母 组成")
     @Size(min = 4, max = 30, message = "用户账号长度为 4-30 个字符")
     @DiffLogField(name = "用户账号")
     private String username;