Upgrade bundler-audit from 0.4.0 to 0.5.0

Bundler Audit can now run check with the `—update` flag to update the
Ruby CVE repository before checking. This removes the need for two
separate commands in GitLab CI.

See the Changelog for more information:
https://github.com/rubysec/bundler-audit/blob/master/ChangeLog.md#050--2
015-02-28

.gitlab-ci.yml

@@ -158,8 +158,7 @@ bundler:audit:
   only:
     - master
   script:
-    - "bundle exec bundle-audit update"
-    - "bundle exec bundle-audit check --ignore OSVDB-115941"
+    - "bundle exec bundle-audit check --update --ignore OSVDB-115941"
   tags:
     - ruby
     - mysql

Gemfile.lock

@@ -99,7 +99,7 @@ GEM
     bullet (5.0.0)
       activesupport (>= 3.0.0)
       uniform_notifier (~> 1.9.0)
-    bundler-audit (0.4.0)
+    bundler-audit (0.5.0)
       bundler (~> 1.2)
       thor (~> 0.18)
     byebug (8.2.1)