minor #16229 [Setup] Change upgrade_patch.rst to reference Symfony 6 (gnito-org)

This PR was merged into the 6.0 branch.

Discussion
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[Setup] Change upgrade_patch.rst to reference Symfony 6

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Commits
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d186765 Change upgrade_patch.rst to reference Symfony 6

Author: javiereguiluz

setup/upgrade_patch.rst

@@ -1,7 +1,7 @@
 .. index::
     single: Upgrading; Patch Version
 
-Upgrading a Patch Version (e.g. 5.0.0 to 5.0.1)
+Upgrading a Patch Version (e.g. 6.0.0 to 6.0.1)
 ===============================================
 
 When a new patch version is released (only the last number changed), it is a