minor #8197 Updated the Requirements article for Symfony 3.4 (javiereguiluz)

This PR was merged into the 3.4 branch.

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Updated the Requirements article for Symfony 3.4

Same as #8142 but for 3.4.

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f09355d Updated the Requirements article for Symfony 3.4

Author: xabbuh

reference/requirements.rst

@@ -6,7 +6,7 @@
 Requirements for Running Symfony
 ================================
 
-Symfony 3.3 requires **PHP 5.5.9** or higher to run, in addition to other minor
+Symfony 3.4 requires **PHP 5.5.9** or higher to run, in addition to other minor
 requirements. To make things simple, Symfony provides a tool to quickly check if
 your system meets all those requirements.