docs: fix anchor link on Ubuntu installation page

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/installation/ubuntulinux.md

@@ -95,7 +95,7 @@ To upgrade your kernel and install the additional packages, do the following:
 
         $ sudo reboot
 
-5. After your system reboots, go ahead and [install Docker](#installing-docker-on-ubuntu).
+5. After your system reboots, go ahead and [install Docker](#installation).
 
 ## Installation