Bump Rails 4 dependencies

We got rid of `Gemfile.rails4.lock` in `master`, but this
stable branch still uses it. To fix this, we just need to run:

```
BUNDLE_GEMFILE=Gemfile.rails4 bundle install
```

Gemfile.rails4.lock

@@ -277,7 +277,7 @@ GEM
       grpc (~> 1.0)
     github-markup (1.7.0)
     gitlab-markup (1.6.5)
-    gitlab-sidekiq-fetcher (0.1.0)
+    gitlab-sidekiq-fetcher (0.4.0)
       sidekiq (~> 5)
     gitlab-styles (2.4.1)
       rubocop (~> 0.54.0)
@@ -1002,7 +1002,7 @@ DEPENDENCIES
   gitaly-proto (~> 1.3.0)
   github-markup (~> 1.7.0)
   gitlab-markup (~> 1.6.5)
-  gitlab-sidekiq-fetcher (~> 0.1.0)
+  gitlab-sidekiq-fetcher (~> 0.4.0)
   gitlab-styles (~> 2.4)
   gitlab_omniauth-ldap (~> 2.0.4)
   gon (~> 6.2)
@@ -1160,4 +1160,4 @@ DEPENDENCIES
   wikicloth (= 0.8.1)
 BUNDLED WITH
-   1.17.1
+   1.17.3