Use the "chef-gem" software instead of "chef"

Hoping this will fix the ohai-chef-chef-config dependency hell.

config/projects/gitlab.rb

@@ -47,7 +47,7 @@ build_iteration Gitlab::BuildIteration.new.build_iteration
 override :ruby, version: '2.1.6'
 override :rubygems, version: '2.2.5', source: { md5: "7701b5bc348d8da41a511ac012a092a8" }
-override :chef, version: '12.4.1'
+override :'chef-gem', version: '12.4.1'
 override :cacerts, version: '2015.09.02', source: { md5: '3e0e6f302bd4f5b94040b8bcee0ffe15' }
 override :openssl, version: '1.0.1p', source: { url: 'https://www.openssl.org/source/openssl-1.0.1p.tar.gz', md5: '7563e92327199e0067ccd0f79f436976' }
@@ -61,7 +61,7 @@ dependency "package-scripts"
 dependency "git"
 dependency "redis"
 dependency "nginx"
-dependency "chef"
+dependency "chef-gem"
 dependency "remote-syslog" if ee
 dependency "logrotate"
 dependency "runit"