Fix flaky test configuration

Author: sarahchen6

buildSrc/src/main/kotlin/datadog.configure-tests.gradle.kts

@@ -107,12 +107,11 @@ tasks.named("check") {
 
 tasks.withType<Test>().configureEach {
   // Flaky tests management for JUnit 5
-  if (testFramework is JUnitPlatformOptions) {
-    val junitPlatform = testFramework as JUnitPlatformOptions
+  (options as? JUnitPlatformOptions)?.apply {
     if (skipFlakyTestsProvider.isPresent) {
-      junitPlatform.excludeTags("flaky")
+      excludeTags("flaky")
     } else if (runFlakyTestsProvider.isPresent) {
-      junitPlatform.includeTags("flaky")
+      includeTags("flaky")
     }
   }