Fix tests that didn't throw exceptions as expected

These tests contained a double nested lambda. Therefore withEnvironmentVariable's execute only executed a Statement that created a Callable instead of executing the Callable. Co-authored-by: Stefan Birkner <mail@stefan-birkner.de>

Author: michaelruocco

src/test/java/com/github/stefanbirkner/systemlambda/WithEnvironmentVariableTest.java

@@ -251,7 +251,7 @@ void after_callable_throws_exception() {
 
 ignoreException(
 () -> withEnvironmentVariable("dummy name", randomValue())
-.execute(() -> (Callable<String>) () -> {
+.execute((Callable<String>) () -> {
 throw new RuntimeException("dummy exception");
 })
 );
@@ -306,7 +306,7 @@ void after_callable_throws_exception() {
 
 ignoreException(
 () -> withEnvironmentVariable("dummy name", randomValue())
-.execute(() -> (Callable<String>) () -> {
+.execute((Callable<String>) () -> {
 throw new RuntimeException("dummy exception");
 })
 );