Revert "去他妈的限制"

This reverts commit 339d6fab82.

src/utils.rs

@@ -57,6 +57,6 @@ pub fn generate_string(len_min: i64, len_max: i64) -> String {
 
 pub fn generate_username(config: &Arc<Configuration>) -> String {
    config.username_prefix().to_string() + generate_string(
-    2,32-config.username_prefix().len() as i64
+    2,16-config.username_prefix().len() as i64
    ).to_string().as_str()
 }