Mention groups and projects indices in documentation of index start command

Bug: Issue 8629
Change-Id: I61317f6485962069729166b601a109706e71a0a1

Documentation/cmd-index-start.txt

diff --git a/Documentation/cmd-index-start.txt b/Documentation/cmd-index-start.txt
index 769360d..5a002f3 100644
--- a/Documentation/cmd-index-start.txt
+++ b/Documentation/cmd-index-start.txt
@@ -34,6 +34,8 @@
   Currently supported values:
     * changes
     * accounts
+    * groups
+    * projects
 
 --force::
   Force an online re-index.