readme: LInux typo

Author: cirosantilli

README.adoc

@@ -3555,7 +3555,7 @@ Looks like a recompile is needed to modify the image...
 * https://superuser.com/questions/736423/changing-kernel-bootsplash-image
 * https://unix.stackexchange.com/questions/153975/how-to-change-boot-logo-in-linux-mint
 
-=== LInux kernel hardening
+=== Linux kernel hardening
 
 Make it harder to get hacked and easier to notice that you were, at the cost of some (small?) runtime overhead.