[4.1] 9c63dbb Correct parameter name

[Federico G. Schwindt]

commit 9c63dbba81423ba581597163915a2392e562fc36
Author: Federico G. Schwindt <fgsch at lodoss.net>
Date:   Tue Jul 28 22:59:37 2015 +0100

    Correct parameter name
    
    This does say something about how much is used though.

diff --git a/doc/sphinx/phk/persistent.rst b/doc/sphinx/phk/persistent.rst
index 6c1d29c..536e406 100644
--- a/doc/sphinx/phk/persistent.rst
+++ b/doc/sphinx/phk/persistent.rst
@@ -16,7 +16,7 @@ it, and we don't presently have the development resources to fix that.
 
 If you think you have these circumstances, you need to specify
 
-	-sdeprecated_persistence
+	-sdeprecated_persistent
 
 in order to use it.