Update plugin org.openapi.generator to v7.13.0 (#13)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

build.gradle

@@ -7,7 +7,7 @@ plugins {
   id 'com.github.ben-manes.versions' version '0.52.0'
   id 'org.sonarqube' version '6.1.0.5360'
 
-  id 'org.openapi.generator' version '7.12.0'
+  id 'org.openapi.generator' version '7.13.0'
   id 'com.diffplug.spotless' version '7.0.3'
 
   /*