Remove redis initializer to prevent deprecation warning being displayed

[mpw5]

What

Changes to the redis gem were causing deprecation warnings to be constantly displayed by sidekiq. We added a redis initializer to suppress those warnings.

The issue with redis has subsequently been fixed however our initializer is now causing the deprecation warning to be displayed when running eg rspec or cucumber from the command line:

Removing the initializer prevents the deprecation warning from being displayed on the command line and does not reintroduce the warning to sidekiq.

Checklist

Before you ask people to review this PR:

• Tests and rubocop should be passing: bundle exec rake
• Github should not be reporting conflicts; you should have recently run git rebase master.
• There should be no unnecessary whitespace changes. These make diffs harder to read and conflicts more likely.
• The PR description should say what you changed and why, with a link to the JIRA story.
• You should have looked at the diff against master and ensured that nothing unexpected is included in your changes.
• You should have checked that the commit messages say why the change was made.