minor #6559 Update lazy_services.rst (hboomsma)

This PR was submitted for the 3.0 branch but it was merged into the 2.7 branch instead (closes #6559).

Discussion
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Update lazy_services.rst

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | ^3.0.0
| Fixed tickets |

�$ composer require ocramius/proxy-manager:~2.0 instead of 1.0

Commits
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1f18702 Update lazy_services.rst

Author: wouterj

components/dependency_injection/lazy_services.rst

@@ -39,8 +39,9 @@ the `ProxyManager bridge`_:
     So, run:
 
     .. code-block:: bash
-
-        $ composer require ocramius/proxy-manager:~1.0
+    
+        $ composer require ocramius/proxy-manager:~1.0 # for PHP 5
+        $ composer require ocramius/proxy-manager:~2.0 # for PHP 7
 
     Afterwards compile your container and check to make sure that you get
     a proxy for your lazy services.