minor symfony#10418 reword note about empty values during validation (xabbuh)

This PR was merged into the 2.8 branch.

Discussion
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reword note about empty values during validation

Commits
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55ab7f4 reword note about empty values during validation

Author: javiereguiluz

reference/constraints/_empty-values-are-valid.rst.inc

@@ -1,7 +1,6 @@
 .. note::
 
-    As with most of the other constraints, ``null`` values and empty strings
-    are considered valid values. Otherwise, in addition to validating this value,
-    you would also be requiring it, making it impossible to be optional. That's
-    why it's common to combine this constraint with
-    :doc:`NotBlank </reference/constraints/NotBlank>`.
+    As with most of the other constraints, ``null`` and empty strings are
+    considered valid values. This is to allow them to be optional values.
+    If the value is mandatory, a common solution is to combine this constraint
+    with :doc:`NotBlank </reference/constraints/NotBlank>`.