Update demo.odin

Author: gingerBill

examples/demo.odin

@@ -730,11 +730,9 @@ explicit_procedure_overloading :: proc() {
 }
 
 main :: proc() {
-	when false {
+	when true {
 		general_stuff();
-	}
 		default_struct_values();
-	when false {
 		union_type();
 		parametric_polymorphism();
 		threading_example();