Fix a typo in Documentation/sysctl/vm.txt

[Kangmin Park]

--- linux/Documentation/sysctl/vm.txt.orig 2017-09-07 00:19:43.260477784 +0900
+++ linux/Documentation/sysctl/vm.txt 2017-09-07 00:19:56.498431846 +0900
@@ -793,7 +793,7 @@ with no ill effects: errors and warnings
 swappiness

 This control is used to define how aggressive the kernel will swap
-memory pages.  Higher values will increase agressiveness, lower values
+memory pages.  Higher values will increase aggressiveness, lower values
 decrease the amount of swap.  A value of 0 instructs the kernel not to
 initiate swap until the amount of free and file-backed pages is less
 than the high water mark in a zone.

Fixes a spelling in documentation.

Signed-off-by: Kangmin Park <l4stpr0gr4m@xxxxxxxxx>