DOC: fixed typo in management.txt

replaced fot -> for
added two periods
diff --git a/doc/management.txt b/doc/management.txt
index 53d8f1d..b54b30c 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -1553,8 +1553,8 @@
   level "admin".
 
 enable dynamic-cookie backend <backend>
-  Enable the generation of dynamic cookies fot the backend <backend>
-  A secret key must also be provided
+  Enable the generation of dynamic cookies for the backend <backend>.
+  A secret key must also be provided.
 
 enable frontend <frontend>
   Resume a frontend which was temporarily stopped. It is possible that some of