[Test] Use rethrow for checked exception in java-written tests

In 9b5a9ccb `throws Exception` was removed from java test sources and
  all checked exceptions were wrapped with `RuntimeException`

But it was forgotten that there is a `rethrow` utility, which doesn't
  wrap exception but makes the javac happy at the same time

compiler/tests-common/tests/org/jetbrains/kotlin/test/KotlinTestUtils.java

@@ -554,7 +554,7 @@ public class KotlinTestUtils {
                         try {
                             FileUtil.writeToFile(testDataFile, newText);
                         } catch (IOException ioException) {
-                            throw new RuntimeException(ioException);
+                            throw ExceptionUtilsKt.rethrow(e);
                         }
                     }
                 }
@@ -585,7 +585,7 @@ public class KotlinTestUtils {
                             try {
                                 FileUtil.writeToFile(testDataFile, newText);
                             } catch (IOException e) {
-                                throw new RuntimeException(e);
+                                throw ExceptionUtilsKt.rethrow(e);
                             }
                         }
                     }