Use immutable type for static declaration

Change-Id: Idf1d165be9ca6e873572dc2e33f4d768122b743d

gerrit-server/src/test/java/com/google/gerrit/server/util/RegexListSearcherTest.java

diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/util/RegexListSearcherTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/util/RegexListSearcherTest.java
index 322484a..dc8c0d8 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/util/RegexListSearcherTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/util/RegexListSearcherTest.java
@@ -24,7 +24,7 @@
 import org.junit.Test;
 
 public class RegexListSearcherTest {
-  private static final List<String> EMPTY = ImmutableList.of();
+  private static final ImmutableList<String> EMPTY = ImmutableList.of();
 
   @Test
   public void emptyList() {