Use apt command instead of apt-get

The "apt" command is newer and provides better experience.

Change-Id: Ic914ce7aed050bace23b6e9ce79ac3717041905b

doc/upstream-training/git.rst

@@ -37,7 +37,7 @@ Linux
 
 For distributions like Debian, Ubuntu, or Mint open a terminal and type::
 
-  sudo apt-get install git
+  sudo apt install git
 
 For distributions like RedHat, Fedora 21 or earlier, or CentOS open a terminal
 and type::
@@ -96,7 +96,7 @@ Linux
 
 For distributions like Debian, Ubuntu, or Mint open a terminal and type::
 
-  sudo apt-get install git-review
+  sudo apt install git-review
 
 For distributions like RedHat, Fedora 21 or earlier, or CentOS open a terminal
 and type::

doc/upstream-training/index.rst

@@ -50,7 +50,7 @@ How to prepare
   4+ GB of RAM.
   Alternatively, you can use your virtual machine on a public cloud.
 * Check that you can ssh from your laptop to the virtual machine
-* Check that :command:`apt-get install` works on the virtual machine
+* Check that :command:`apt install` works on the virtual machine
 * Read and complete the :doc:`irc` guide.
 * Read and complete the :doc:`accounts` guide.
 * Read and complete the :doc:`git` guide.

doc/upstream-training/irc.rst

@@ -12,7 +12,7 @@ We'll install an IRC program called Hexchat.
 For a linux distrubtions like Debian, Ubuntu, or Mint open a terminal and
 type::
 
-  sudo apt-get install hexchat
+  sudo apt install hexchat
 
 For a linux distrubtions like Redhat, Fedora 21 or earlier, or Centos open
 a terminal and type::

doc/upstream-training/source/14-gerrit.rst

@@ -37,7 +37,7 @@ git config
 Install git review
 ==================
 
-- apt-get / yum / pip install … git review
+- apt / yum / pip install … git review
 
 .. image:: ./_assets/14-05-install.png