DOC: fixed typo in management.txt

replaced fot -> for
added two periods

(cherry picked from commit 25a1c8e4539c12c19a3fe04aabe563cdac5e36db)
Signed-off-by: Willy Tarreau <w@1wt.eu>
diff --git a/doc/management.txt b/doc/management.txt
index 616a040..ad6011e 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -1549,8 +1549,8 @@
   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