Add Etag caching for Pipeline#Show action

Due to a typo this was not actually the case. Now that is fixed and
performance should improve because of this.

lib/gitlab/etag_caching/router.rb

@@ -38,7 +38,7 @@ module Gitlab
           'project_pipelines'
         ),
         Gitlab::EtagCaching::Router::Route.new(
-          %r(^(?!.*(#{RESERVED_WORDS})).*/pipelines/\d+\.json\z),
+          %r(^(?!.*(#{RESERVED_WORDS_REGEX})).*/pipelines/\d+\.json\z),
           'project_pipeline'
         )
       ].freeze

spec/lib/gitlab/etag_caching/router_spec.rb

@@ -77,6 +77,17 @@ describe Gitlab::EtagCaching::Router do
     expect(result).to be_blank
   end
 
+  it 'matches pipeline#show endpoint' do
+    env = build_env(
+      '/my-group/my-project/pipelines/2.json'
+    )
+
+    result = described_class.match(env)
+
+    expect(result).to be_present
+    expect(result.name).to eq 'project_pipeline'
+  end
+
   def build_env(path)
     { 'PATH_INFO' => path }
   end