RefUpdateUtilRepoTest: simplify setup of @Parameters

When using only one test parameter we can return just an array of
parameter values, no need to wrap then in an array.

Release-Notes: skip
Change-Id: I0ae58fa60a838bcb5055b69ac25c9f20e966979b
diff --git a/javatests/com/google/gerrit/git/RefUpdateUtilRepoTest.java b/javatests/com/google/gerrit/git/RefUpdateUtilRepoTest.java
index 60b90f3..a106aa1 100644
--- a/javatests/com/google/gerrit/git/RefUpdateUtilRepoTest.java
+++ b/javatests/com/google/gerrit/git/RefUpdateUtilRepoTest.java
@@ -16,7 +16,6 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.common.collect.ImmutableList;
 import com.google.common.io.MoreFiles;
 import com.google.common.io.RecursiveDeleteOption;
 import java.nio.file.Files;
@@ -77,8 +76,8 @@
   }
 
   @Parameters(name = "{0}")
-  public static ImmutableList<RepoSetup[]> data() {
-    return ImmutableList.copyOf(new RepoSetup[][] {{RepoSetup.LOCAL_DISK}, {RepoSetup.IN_MEMORY}});
+  public static RepoSetup[] data() {
+    return new RepoSetup[] {RepoSetup.LOCAL_DISK, RepoSetup.IN_MEMORY};
   }
 
   @Parameter public RepoSetup repoSetup;