minor symfony#4854 Removed no longer needed information about PHP 5.3 (WouterJ)

This PR was merged into the 2.3 branch.

Discussion
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Removed no longer needed information about PHP 5.3

While merging, symfony#4753, I thought we could remove these things completely from the docs, as PHP 5.3 and namespacing are quite common now.

| Q   | A
| --- | ---
| Doc fix? | yes
| New docs? | no
| Applies to | all
| Fixed tickets | -

Commits
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b6636ae Removed no longer needed information about PHP 5.3

Author: weaverryan

book/controller.rst

@@ -116,7 +116,7 @@ Controllers are also called *actions*.
 
 This controller is pretty straightforward:
 
-* *line 4*: Symfony takes advantage of PHP 5.3 namespace functionality to
+* *line 4*: Symfony takes advantage of PHP's namespace functionality to
   namespace the entire controller class. The ``use`` keyword imports the
   ``Response`` class, which the controller must return.
 

cookbook/bundles/best_practices.rst

@@ -29,10 +29,9 @@ Bundle Name
 -----------
 
 A bundle is also a PHP namespace. The namespace must follow the technical
-interoperability `standards`_ for PHP 5.3 namespaces and class names: it
-starts with a vendor segment, followed by zero or more category segments, and
-it ends with the namespace short name, which must end with a ``Bundle``
-suffix.
+interoperability `standards`_ for PHP namespaces and class names: it starts
+with a vendor segment, followed by zero or more category segments, and it ends
+with the namespace short name, which must end with a ``Bundle`` suffix.
 
 A namespace becomes a bundle as soon as you add a bundle class to it. The
 bundle class name must follow these simple rules:

cookbook/logging/monolog.rst

@@ -4,8 +4,8 @@
 How to Use Monolog to Write Logs
 ================================
 
-Monolog_ is a logging library for PHP 5.3 used by Symfony. It is
-inspired by the Python LogBook library.
+Monolog_ is a logging library for PHP used by Symfony. It is inspired by the
+Python LogBook library.
 
 Usage
 -----