fix(*): ruby version was updated in .ruby-version but not Vagrant. Make them match (#1502)

Vagrantfile

@@ -46,12 +46,12 @@ git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
 export PATH="$HOME/.rbenv/bin::$PATH"
 eval "$(rbenv init -)"
 
-echo "Compiling Ruby 2.3.1: warning, this takes a while!!!"
-rbenv install 2.3.1
-rbenv global 2.3.1
-
 cd /vagrant
 
+echo "Compiling Ruby $(cat .ruby-version): warning, this takes a while!!!"
+rbenv install $(cat .ruby-version)
+rbenv global $(cat .ruby-version)
+
 # Configure database
 sudo -u postgres createuser -U postgres vagrant -s
 sudo -u postgres createdb -U postgres mastodon_development