Fix CheckedRunnableTest#shouldApplyAnUncheckedFunctionThatThrows (#2954)

* `shouldApplyAnUncheckedFunctionThatThrows` always passed, when
removing the `throw new Error()` because the failed asserting was
immediately caught.

```java
        final Runnable runnable = CheckedRunnable.of(() -> { /*throw new Error();*/ }).unchecked(); // Test would still pass
```

Fixed by using `assertThrows` from JUnit

Author: bvkatwijk

src/test/java/io/vavr/CheckedRunnableTest.java

@@ -65,11 +65,6 @@ public void shouldApplyAnUncheckedFunctionThatDoesNotThrow() {
     @Test
     public void shouldApplyAnUncheckedFunctionThatThrows() {
         final Runnable runnable = CheckedRunnable.of(() -> { throw new Error(); }).unchecked();
-        try {
-            runnable.run();
-            Assertions.fail("Did expect an exception.");
-        } catch(Error x) {
-            // ok!
-        }
+        Assertions.assertThrows(Error.class, () -> runnable.run());
     }
 }