Change to https link.

Author: HonkingGoose

book/01-introduction/sections/installing.asc

@@ -29,7 +29,7 @@ If you're on a Debian-based distribution, such as Ubuntu, try `apt`:
 $ sudo apt install git-all
 ----
 
-For more options, there are instructions for installing on several different Unix distributions on the Git website, at http://git-scm.com/download/linux[].
+For more options, there are instructions for installing on several different Unix distributions on the Git website, at https://git-scm.com/download/linux[].
 
 ==== Installing on macOS