minor #17526 Add comma (dragonito)

This PR was submitted for the 6.2 branch but it was merged into the 5.4 branch instead.

Discussion
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Add comma

Just found a missing comma in this text

Commits
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06374e8 Add comma

Author: javiereguiluz

components/validator/resources.rst

@@ -76,7 +76,7 @@ configure the locations of these files::
 
 .. note::
 
-    If you want to load YAML mapping files then you will also need to install
+    If you want to load YAML mapping files, then you will also need to install
     :doc:`the Yaml component </components/yaml>`.
 
 .. tip::