Try to remove rdoc

Gemfile

@@ -142,7 +142,6 @@ gem 'gitlab-markup', '~> 1.7.0'
 gem 'github-markup', '~> 1.7.0', require: 'github/markup'
 gem 'commonmarker', '~> 0.20'
 gem 'RedCloth', '~> 4.3.2'
-gem 'rdoc', '~> 6.1.2'
 gem 'org-ruby', '~> 0.9.12'
 gem 'creole', '~> 0.5.0'
 gem 'wikicloth', '0.8.1'

Gemfile.lock

@@ -822,7 +822,6 @@ GEM
       ffi (>= 1.0.6)
       msgpack (>= 0.4.3)
       optimist (>= 3.0.0)
-    rdoc (6.1.2)
     re2 (1.1.1)
     recaptcha (4.13.1)
       json
@@ -1305,7 +1304,6 @@ DEPENDENCIES
   raindrops (~> 0.18)
   rblineprof (~> 0.3.6)
   rbtrace (~> 0.4)
-  rdoc (~> 6.1.2)
   re2 (~> 1.1.1)
   recaptcha (~> 4.11)
   redis (~> 4.0)