Bump Rubocop TargetRubyVersion to 2.5 series

Ruby 2.4 is EOL and Rubocop has accordingly dropped their support.

https://www.ruby-lang.org/en/news/2020/04/05/support-of-ruby-2-4-has-ended/
rubocop/rubocop#9648
https://github.com/rubocop/rubocop/blob/76bc0a0e026b13fccdc7b6bccfd6d082d24a7b52/CHANGELOG.md#1130-2021-04-20

The change to the TargetRubyVersion introduced a violation because of
the redundant `begin`, which has been autocorrected.

.rubocop.yml

@@ -2,7 +2,7 @@ inherit_gem:
   rubocop-shopify: rubocop.yml
 
 AllCops:
-  TargetRubyVersion: 2.4.4
+  TargetRubyVersion: 2.5.9
   Exclude:
     - 'vendor/bundle/**/*'
 Lint/SuppressedException:

lib/job-iteration.rb

@@ -38,16 +38,14 @@ module JobIteration
   def load_integrations
     loaded = nil
     INTEGRATIONS.each do |integration|
-      begin
-        load_integration(integration)
-        if loaded
-          raise IntegrationLoadError,
-            "#{loaded} integration has already been loaded, but #{integration} is also available. " \
-            "Iteration will only work with one integration."
-        end
-        loaded = integration
-      rescue LoadError
+      load_integration(integration)
+      if loaded
+        raise IntegrationLoadError,
+          "#{loaded} integration has already been loaded, but #{integration} is also available. " \
+          "Iteration will only work with one integration."
       end
+      loaded = integration
+    rescue LoadError
     end
   end