Add missing article "the" in access-control.txt

This patch adds a missing article "the" in a documentation
sentence in access-control.txt.

Change-Id: I12a1bd73f121cb0441554ec3afd6a0a700d35e32

Documentation/access-control.txt

diff --git a/Documentation/access-control.txt b/Documentation/access-control.txt
index 4099ed4..8b2fd64 100644
--- a/Documentation/access-control.txt
+++ b/Documentation/access-control.txt
@@ -9,7 +9,7 @@
 [[system_groups]]
 == System Groups
 
-Gerrit comes with following system groups:
+Gerrit comes with the following system groups:
 
 * Administrators
 * Anonymous Users