Revert "vagrant: use ruby 2.2"

This reverts commit c00405d8d9bab331055f202f61ac117900454f36.

pkgs/top-level/all-packages.nix

···
   uncrustify = callPackage ../development/tools/misc/uncrustify { };
 
   vagrant = callPackage ../development/tools/vagrant {
-    ruby = ruby_2_2_2;
+    ruby = ruby_2_0_0;
   };
 
   gdb = callPackage ../development/tools/misc/gdb {