Add net-ldap explicitly since we use it directly

And this has already been done on EE, so it’ll match now.

Gemfile

@@ -62,6 +62,7 @@ gem 'browser', '~> 2.2'
 # GitLab fork with several improvements to original library. For full list of changes
 # see https://github.com/intridea/omniauth-ldap/compare/master...gitlabhq:master
 gem 'gitlab_omniauth-ldap', '~> 2.0.2', require: 'omniauth-ldap'
+gem 'net-ldap'
 
 # Git Wiki
 # Required manually in config/initializers/gollum.rb to control load order

Gemfile.lock

@@ -1013,6 +1013,7 @@ DEPENDENCIES
   minitest (~> 5.7.0)
   mousetrap-rails (~> 1.4.6)
   mysql2 (~> 0.4.5)
+  net-ldap
   nokogiri (~> 1.6.7, >= 1.6.7.2)
   oauth2 (~> 1.4)
   octokit (~> 4.6.2)