Adapt to upstream changes

gitiles changed the signature of GitilesAccess::ListRepositories slightly.
(https://gerrit-review.googlesource.com/#/c/70420/2)

Change-Id: I3155d231f17c00ebb2f32c73e3f3f12e1ca2ab64

src/main/java/com/googlesource/gerrit/plugins/gitiles/GerritGitilesAccess.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/gitiles/GerritGitilesAccess.java b/src/main/java/com/googlesource/gerrit/plugins/gitiles/GerritGitilesAccess.java
index 9234736..dc97bc6 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/gitiles/GerritGitilesAccess.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/gitiles/GerritGitilesAccess.java
@@ -15,6 +15,7 @@
 package com.googlesource.gerrit.plugins.gitiles;
 
 import com.google.common.collect.Maps;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.common.ProjectInfo;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.reviewdb.client.Project;
@@ -96,8 +97,8 @@
 
   @Override
   public Map<String, RepositoryDescription> listRepositories(
-      Set<String> branches) throws ServiceNotEnabledException,
-      ServiceNotAuthorizedException, IOException {
+      @Nullable String prefix, Set<String> branches) throws ServiceNotEnabledException,
+      ServiceNotAuthorizedException, IOException  {
     ListProjects lp = listProjects.get();
     lp.setShowDescription(true);
     lp.setAll(true);