Fix typo in VarDumper README

Author: WouterSioen

src/Symfony/Component/VarDumper/README.md

@@ -2,7 +2,7 @@ VarDumper Component
 ===================
 
 The VarDumper component provides mechanisms for walking through any arbitrary
-PHP variable. Built on top, it provides a better `dump()`` function that you
+PHP variable. Built on top, it provides a better `dump()` function that you
 can use instead of `var_dump`.
 
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