Fix failing build due to deprecation of initialCaps (#2168)

Include functional for failing build in debian

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppQt5AbstractCodegen.java

@@ -204,7 +204,7 @@ public class CppQt5AbstractCodegen extends AbstractCppCodegen implements Codegen
 
     @Override
     public String toModelFilename(String name) {
-        return modelNamePrefix + sanitizeName(initialCaps(name));
+        return toModelName(name);
     }
     
     /**