remove ALLOW_PLANTUML_INCLUDE + update to 1.2023.9

- update Plantuml to v1.2023.9
- PlantUML core removed `OptionFlags.ALLOW_INCLUDE` and uses now the `PLANTUML_SECURITY_PROFILE`

src/main/java/net/sourceforge/plantuml/servlet/DiagramResponse.java

@@ -111,11 +111,6 @@ public class DiagramResponse {
             return;
         }
         initialized = true;
-        // set allow include to false by default
-        OptionFlags.ALLOW_INCLUDE = false;
-        if ("true".equalsIgnoreCase(System.getenv("ALLOW_PLANTUML_INCLUDE"))) {
-            OptionFlags.ALLOW_INCLUDE = true;
-        }
         // set security profile to INTERNET by default
         // NOTE: this property is cached inside PlantUML and cannot be changed after the first call of PlantUML
         System.setProperty("PLANTUML_SECURITY_PROFILE", SecurityProfile.INTERNET.toString());