minor #4721 [Cookbook][Composer] fix note directive (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Cookbook][Composer] fix note directive

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

Commits
-------

2186ec6 fix note directive

cookbook/composer.rst

@@ -17,7 +17,7 @@ To install Composer on Linux or Mac OS X, execute the following two commands:
     $ curl -sS https://getcomposer.org/installer | php
     $ sudo mv composer.phar /usr/local/bin/composer
 
--.. note::
+.. note::
 
     If you don't have ``curl`` installed, you can also just download the
     ``installer`` file manually at http://getcomposer.org/installer and