Fixed the RST syntax

Author: javiereguiluz

service_container/parameters.rst

@@ -253,7 +253,7 @@ key and define the type as ``constant``.
 
     YAML files can refer to PHP constants via the ``@=constant('CONSTANT_NAME')``
     syntax, which is provided by the
-    :doc:`Expression Language component /components/expression_language`. See
+    :doc:`Expression Language component </components/expression_language>`. See
     :doc:`/components/expression_language/syntax` to learn more about its syntax.
 
 .. tip::