Merge pull request #16004 from JuanitoFatas/doc/patch-1

[ci skip] Add missing prologue section of upgrading ruby on rails guide.

guides/source/upgrading_ruby_on_rails.md

@@ -3,6 +3,8 @@ A Guide for Upgrading Ruby on Rails
 
 This guide provides steps to be followed when you upgrade your applications to a newer version of Ruby on Rails. These steps are also available in individual release guides.
 
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+
 General Advice
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