minor #6777 fix code block indentation (xabbuh)

This PR was merged into the 2.7 branch.

Discussion
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fix code block indentation

Commits
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4e73a55 fix code block indentation

Author: xabbuh

service_container/service_decoration.rst

@@ -125,11 +125,11 @@ convention, the old ``app.mailer`` service is renamed to
 
         .. code-block:: yaml
 
-        services:
-            app.mailer:
-                # ...
-                decoration_inner_name: app.decorating_mailer.wooz
-                arguments: ['@app.decorating_mailer.wooz']
+            services:
+                app.mailer:
+                    # ...
+                    decoration_inner_name: app.decorating_mailer.wooz
+                    arguments: ['@app.decorating_mailer.wooz']
 
         .. code-block:: xml