Remove note for documentation changes to not run CI

Since CI also runs spellcheck we should always run it.

See: rails#42615 (comment)

Author: zzak

guides/source/contributing_to_ruby_on_rails.md

@@ -140,8 +140,6 @@ To do so, make changes to Rails guides source files (located [here](https://gith
 
 When working with documentation, please take into account the [API Documentation Guidelines](api_documentation_guidelines.html) and the [Ruby on Rails Guides Guidelines](ruby_on_rails_guides_guidelines.html).
 
-NOTE: For documentation changes, your pull request title should include [ci skip]. This will skip running the test suite, helping us to cut down on our server costs. Keep in mind that you should only skip CI when your change touches documentation exclusively.
-
 Translating Rails Guides
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