Update dependencies, Install rspec-retry for flaky tests (#897)

* Update dependencies

- update puma to ~> 5.5 in Gemfile
- update sidekiq to ~> 5.2 in Gemfile
- run `bundle update`

* Install rspec-retry for flaky tests

Gemfile

@@ -27,7 +27,7 @@ gem 'loofah', '>= 2.2.3'
 gem 'mysql2', '~> 0.5'
 gem 'pkg-config', '~> 1.1'
 # Use Puma as the app server
-gem 'puma', '~> 4.3'
+gem 'puma', '~> 5.5'
 gem 'rack', '>= 2.0.6'
 gem 'rails', '~> 5.1.6'
 gem 'redcarpet'
@@ -38,7 +38,7 @@ gem 'rollbar'
 gem 'rsolr', '>= 1.0'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
-gem 'sidekiq', '~> 5.1.3'
+gem 'sidekiq', '~> 5.2'
 gem 'sidekiq-failures'
 gem 'sidekiq-status'
 # Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
@@ -83,3 +83,7 @@ group :development, :test do
   gem 'webmock'
   gem 'xray-rails'
 end
+
+group :test do
+  gem 'rspec-retry' # Unlike rspec, this doesn't need to be included in development group
+end