Update a typo in style_guides.md

doc/development/contributing/style_guides.md

@@ -30,7 +30,7 @@ Our codebase style is defined and enforced by [RuboCop](https://github.com/ruboc
 You can check for any offenses locally with `bundle exec rubocop --parallel`.
 On the CI, this is automatically checked by the `static-analysis` jobs.
 
-For RuboCop rules that we have not taken a decision yet, we follow the
+For RuboCop rules that we have not taken a decision on yet, we follow the
 [Ruby Style Guide](https://github.com/rubocop-hq/ruby-style-guide),
 [Rails Style Guide](https://github.com/rubocop-hq/rails-style-guide), and
 [RSpec Style Guide](https://github.com/rubocop-hq/rspec-style-guide) as general