VisibilityChecker: use #areAllReachable with a stream of starters

The variant of #areAllReachable receiving the starters as a Collection
is deprecated. Use the suggested alternative that receive them as
Stream.

The deprecated version will be removed in JGit 7.0

Change-Id: If24e8f2c98edfdcfefc0c628c4c754709f54a5c5

java/com/google/gitiles/VisibilityChecker.java

diff --git a/java/com/google/gitiles/VisibilityChecker.java b/java/com/google/gitiles/VisibilityChecker.java
index fd81396..dedf547 100644
--- a/java/com/google/gitiles/VisibilityChecker.java
+++ b/java/com/google/gitiles/VisibilityChecker.java
@@ -68,8 +68,8 @@
       return false;
     }
 
-    return !walk.createReachabilityChecker()
-        .areAllReachable(ImmutableList.of(commit), startCommits)
+    return !walk.getObjectReader().createReachabilityChecker(walk)
+        .areAllReachable(ImmutableList.of(commit), startCommits.stream())
         .isPresent();
   }