test: migrate remaining junit 4 assertion leftovers to junit 5

- gateway-core HttpEndpointInvokerTest: junit.framework.AssertionFailedError -> org.opentest4j.AssertionFailedError
- repository-test SubscriptionRepositoryTest: assertEquals message argument moved to the junit 5 last-arg position

Author: phiz71

gravitee-apim-gateway/gravitee-apim-gateway-core/src/test/java/io/gravitee/gateway/reactive/core/v4/invoker/HttpEndpointInvokerTest.java

@@ -41,7 +41,6 @@
 import io.reactivex.rxjava3.observers.TestObserver;
 import java.util.List;
 import java.util.stream.Stream;
-import junit.framework.AssertionFailedError;
 import org.assertj.core.api.Assertions;
 import org.assertj.core.api.InstanceOfAssertFactory;
 import org.junit.jupiter.api.BeforeEach;
@@ -53,6 +52,7 @@
 import org.junit.jupiter.params.provider.ValueSource;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.opentest4j.AssertionFailedError;
 
 /**
  * @author Jeoffrey HAEYAERT (jeoffrey.haeyaert at graviteesource.com)

gravitee-apim-repository/gravitee-apim-repository-test/src/test/java/io/gravitee/repository/management/SubscriptionRepositoryTest.java

@@ -831,11 +831,11 @@ public void searchAfter_shouldPaginateByIdOnlyFallback() throws TechnicalExcepti
 
         // Keyset pagination must reproduce the single-page order exactly — same elements, same order,
         // no skips or duplicates. This holds only when the seek predicate agrees with the sort.
-        assertEquals("id-only keyset pagination must reproduce the single-page id order (no skip/dup/reorder)", singlePageOrder, paged);
+        assertEquals(singlePageOrder, paged, "id-only keyset pagination must reproduce the single-page id order (no skip/dup/reorder)");
         assertEquals(
-            "plan3 subs returned exactly — no leak from unrelated plans",
             Set.of("sub-legacy-push", "sub2", "sub3", "sub6", "sub7", "sub8"),
-            new java.util.HashSet<>(paged)
+            new java.util.HashSet<>(paged),
+            "plan3 subs returned exactly — no leak from unrelated plans"
         );
     }