[Core] Remove usage of since Collectors.toUnmodifiableList (#2531)

Collectors.toUnmodifiableList was introduced since java 10.
Which is slightly too modern for us to use.

Fixes #2530

Author: mpkorstanje

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Removed
 
 ### Fixed
+ - [Core] Removed usage of since Java 10 `Collectors.toUnmodifiableList()` method ([#2531](https://github.com/cucumber/cucumber-jvm/pull/2531) M.P. Korstanje) 
 
 ## [7.3.0] (2022-04-19)
 

gherkin-messages/src/main/java/io/cucumber/core/gherkin/messages/GherkinMessagesFeatureParser.java

@@ -17,7 +17,6 @@
 import java.util.Optional;
 import java.util.UUID;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 import static io.cucumber.messages.types.SourceMediaType.TEXT_X_CUCUMBER_GHERKIN_PLAIN;
 import static java.util.stream.Collectors.toList;
@@ -30,7 +29,7 @@ public Optional<Feature> parse(URI path, String source, Supplier<UUID> idGenerat
                 .idGenerator(() -> idGenerator.get().toString())
                 .build()
                 .parse(Envelope.of(new Source(path.toString(), source, TEXT_X_CUCUMBER_GHERKIN_PLAIN)))
-                .collect(Collectors.toUnmodifiableList());
+                .collect(toList());
 
         List<String> errors = envelopes.stream()
                 .map(Envelope::getParseError)