Remove python from installation docs

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

config/initializers/3_grit_ext.rb

 require 'grit'
-require 'pygments'
 
 Grit::Git.git_binary = Gitlab.config.git.bin_path
 Grit::Git.git_timeout = Gitlab.config.git.timeout

doc/install/installation.md

@@ -56,23 +56,6 @@ Install the required packages:
 
     sudo apt-get install -y build-essential zlib1g-dev libyaml-dev libssl-dev libgdbm-dev libreadline-dev libncurses5-dev libffi-dev curl openssh-server redis-server checkinstall libxml2-dev libxslt-dev libcurl4-openssl-dev libicu-dev logrotate
 
-Make sure you have the right version of Python installed.
-
-    # Install Python
-    sudo apt-get install -y python
-
-    # Make sure that Python is 2.5+ (3.x is not supported at the moment)
-    python --version
-
-    # If it's Python 3 you might need to install Python 2 separately
-    sudo apt-get install -y python2.7
-
-    # Make sure you can access Python via python2
-    python2 --version
-
-    # If you get a "command not found" error create a link to the python binary
-    sudo ln -s /usr/bin/python /usr/bin/python2
-
     # For reStructuredText markup language support install required package:
     sudo apt-get install -y python-docutils