Upgrade Gradle game template Gradle 8.4 -> 8.6

jme3-templates/src/com/jme3/gde/templates/files/freemarker/build.gradle.ftl

@@ -119,5 +119,5 @@ java {
 }
 
 wrapper {
-    gradleVersion = '8.4'
+    gradleVersion = '8.6'
 }