Documentation/sysctl/vm.txt typo

Fix trivial typo: duplicated word.
Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Documentation/sysctl/vm.txt

@@ -196,7 +196,7 @@ controlled by this knob are discussed in Documentation/laptops/laptop-mode.txt.
 
 legacy_va_layout
 
-If non-zero, this sysctl disables the new 32-bit mmap mmap layout - the kernel
+If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel
 will use the legacy (2.4) layout for all processes.
 
 ==============================================================