removed an unused import statement

Author: gregory-at-cvs

android-agent/src/test/kotlin/io/opentelemetry/android/agent/session/SessionManagerTest.kt

@@ -22,7 +22,6 @@ import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertAll
 import java.util.concurrent.CountDownLatch
-import java.util.concurrent.ExecutorService
 import java.util.concurrent.Executors
 import java.util.concurrent.TimeUnit
 import java.util.concurrent.atomic.AtomicInteger