Make functionalTest aware of new gradle version we use in github actions

Author: dnestoro

build-logic/gradle-functional-testing/src/main/groovy/org.graalvm.build.functional-testing.gradle

@@ -84,7 +84,7 @@ def graalVm = javaToolchains.launcherFor {
 def fullFunctionalTest = tasks.register("fullFunctionalTest")
 
 ['functionalTest', 'configCacheFunctionalTest'].each { baseName ->
-    ["current", "7.4", "7.6.2", "8.0.1", "8.2.1"].each { gradleVersion ->
+    ["current", "7.4", "7.6.2", "8.0.1", "8.2.1", "8.13"].each { gradleVersion ->
         String taskName = gradleVersion == 'current' ? baseName : "gradle${gradleVersion}${baseName.capitalize()}"
         // Add a task to run the functional tests
         def testTask = tasks.register(taskName, Test) {