fix: SelectItem generics

- fixes #2196

Signed-off-by: Andreas Reichel <[email protected]>

Author: manticore-projects

src/main/java/net/sf/jsqlparser/statement/select/SelectItem.java

@@ -101,7 +101,7 @@ public SelectItem<T> withExpression(T expression) {
         return this;
     }
 
-    public SelectItem<?> withAlias(Alias alias) {
+    public SelectItem<T> withAlias(Alias alias) {
         this.setAlias(alias);
         return this;
     }