minor #9906 Minor typo in csrf.rst (lmlsna)

This PR was submitted for the 4.1 branch but it was merged into the 4.0 branch instead (closes #9906).

Discussion
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Minor typo in csrf.rst

Add a "do"

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Commits
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222af71 Minor typo in csrf.rst

Author: javiereguiluz

security/csrf.rst

@@ -59,7 +59,7 @@ CSRF Protection in Symfony Forms
 --------------------------------
 
 Forms created with the Symfony Form component include CSRF tokens by default
-and Symfony checks them automatically, so you don't have to anything to be
+and Symfony checks them automatically, so you don't have to do anything to be
 protected against CSRF attacks.
 
 .. _form-csrf-customization: