Remove colons from section names

Collapsible sections use colons as a separator, so we replace them in
the name with hyphens.

lib/gitlab/util.rb

@@ -24,6 +24,8 @@ module Gitlab
       def section_start(name, description = name)
         return unless ENV['CI']
+        name.tr!(':', '-')
+
         @section_name = name
         $stdout.puts "section_start:#{Time.now.to_i}:#{name}\r\e[0K#{description}"
       end