Remove unused `gitlab:generate_docs` Rake task

This was the only thing using the `sdoc` gem, which was blocking another
gem from updating.

1 files changed, 0 insertions, 3 deletions

diff --git a/Gemfile b/Gemfile
index af82ae16a56..3235e7af98e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -260,9 +260,6 @@ group :development do
   gem 'better_errors', '~> 1.0.1'
   gem 'binding_of_caller', '~> 0.7.2'
 
-  # Docs generator
-  gem 'sdoc', '~> 0.3.20'
-
   # thin instead webrick
   gem 'thin', '~> 1.7.0'
 end