Make function open to overrie it IDE specific part

Namely, this function is overrided in 211 & 212 platforms, see ScriptDefinitionsManager

plugins/scripting/scripting-compiler-impl/src/org/jetbrains/kotlin/scripting/definitions/LazyScriptDefinitionProvider.kt

@@ -61,7 +61,7 @@ abstract class LazyScriptDefinitionProvider : ScriptDefinitionProvider {
         }
     }
 
-    protected fun dispose() {
+    protected open fun dispose() {
         disposed = true
         clearCache()
     }