DOC: missing track-sc* in http-request rules

track-sc is well defined in http-request rules, but not listed in
option list.
This patch fix this miss.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index f7776a9..c0aeb3a 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -2916,7 +2916,8 @@
               add-acl(<file name>) <key fmt> |
               del-acl(<file name>) <key fmt> |
               del-map(<file name>) <key fmt> |
-              set-map(<file name>) <key fmt> <value fmt>
+              set-map(<file name>) <key fmt> <value fmt> |
+              { track-sc0 | track-sc1 | track-sc2 } <key> [table <table>]
              }
              [ { if | unless } <condition> ]
   Access control for Layer 7 requests