apt: added to description.

Added that apt should be preferred over apt-get in Ubuntu systems which are 16.04 and later.

pages/linux/apt.md

@@ -1,6 +1,7 @@
 # apt
 
 > Package management utility for Debian based distributions.
+> Recommended replacement for apt-get in Ubuntu versions 16.04 and later.
 
 - Update the list of available packages and versions (it's recommended to run this before other `apt` commands):