minor #4751 [BestPractices] fix alignment of YAML values (xelaris)

This PR was merged into the 2.3 branch.

Discussion
----------

[BestPractices] fix alignment of YAML values

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3+
| Fixed tickets |

Commits
-------

f49ac99 [BestPractices] fix alignment of YAML values

best_practices/templates.rst

@@ -153,7 +153,7 @@ name is irrelevant because you never use it in your own code):
         app.twig.app_extension:
             class:     AppBundle\Twig\AppExtension
             arguments: ["@markdown"]
-            public: false
+            public:    false
             tags:
                 - { name: twig.extension }