fix JUnit imports

Author: eric-milles

src/test/groovy/BreakContinueLabelTest.groovy

@@ -18,9 +18,9 @@
  */
 package groovy
 
-import org.junit.jupiter.api.Test
+import org.junit.Test
 
-import static org.junit.jupiter.api.Assertions.fail
+import static org.junit.Assert.fail
 
 final class BreakContinueLabelTest {