"repo download" supports authentication

Override isAuthSupported to ensure "repo download" download commands
are shown even for changes that are not visible to anonymous users.

Change-Id: Ie9ee653508c4cd9b4cd85d1756ab657c7b3f7d1e

src/main/java/com/googlesource/gerrit/plugins/download/scheme/RepoScheme.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/download/scheme/RepoScheme.java b/src/main/java/com/googlesource/gerrit/plugins/download/scheme/RepoScheme.java
index 9147d12..7397b0a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/download/scheme/RepoScheme.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/download/scheme/RepoScheme.java
@@ -45,4 +45,9 @@
   public boolean isAuthRequired() {
     return false;
   }
+
+  @Override
+  public boolean isAuthSupported() {
+    return true;
+  }
 }