patch 8.1.1401: misspelled mkspellmem as makespellmem

Problem:    Misspelled mkspellmem as makespellmem.
Solution:   Drop duplicate help entry, fix test. (Naruhiko Nishino, Ken
            Takata, closes #4437)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index e7bb4fd..fd2ae6a 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4913,12 +4913,6 @@
 <	This option cannot be set from a |modeline| or in the |sandbox|, for
 	security reasons.
 
-						*'makespellmem'* *'msm'*
-'makespellmem' 'msm'		string	(default "460000,2000,500")
-			global
-	Values relevant only when compressing a spell file, see |spell|.
-	This option cannot be set from a |modeline| or in the |sandbox|.
-
 						*'matchpairs'* *'mps'*
 'matchpairs' 'mps'	string	(default "(:),{:},[:]")
 			local to buffer
@@ -5070,6 +5064,8 @@
 <	If you have less than 512 Mbyte |:mkspell| may fail for some
 	languages, no matter what you set 'mkspellmem' to.
 
+	This option cannot be set from a |modeline| or in the |sandbox|.
+
 				   *'modeline'* *'ml'* *'nomodeline'* *'noml'*
 'modeline' 'ml'		boolean	(Vim default: on (off for root),
 				 Vi default: off)