Mentioned the "Symfony Upgrade Fixer" in the upgrade article

Author: javiereguiluz

setup/upgrade_major.rst

@@ -4,10 +4,10 @@
 Upgrading a Major Version (e.g. 2.7.0 to 3.0.0)
 ===============================================
 
-Every few years, Symfony releases a new major version release (the first number
-changes). These releases are the trickiest to upgrade, as they are allowed to
-contain BC breaks. However, Symfony tries to make this upgrade process as
-smooth as possible.
+Every two years, Symfony releases a new major version release (the first number
+changes). These releases are the trickiest to upgrade, as they are allowed break
+backwards compatibility. However, Symfony makes this upgrade process as smooth
+as possible.
 
 This means that you can update most of your code before the major release is
 actually released. This is called making your code *future compatible*.
@@ -113,6 +113,12 @@ done!
 
     (you can also execute the command like ``SYMFONY_DEPRECATIONS_HELPER=weak phpunit``).
 
+.. tip::
+
+    Some members of the Symfony Community have developed a tool called
+    `Symfony-Upgrade-Fixer`_ which fixes some of the most common deprecations
+    automatically and can save you a lot of work.
+
 .. _upgrade-major-symfony-composer:
 
 2) Update to the New Major Version via Composer
@@ -152,3 +158,5 @@ There is a good chance that you're done now! However, the next major version
 Make sure you read the ``UPGRADE-X.0.md`` (where X is the new major version)
 included in the Symfony repository for any BC break that you need to be aware
 of.
+
+.. _`Symfony-Upgrade-Fixer`: https://github.com/umpirsky/Symfony-Upgrade-Fixer