minor symfony#5720 adding closing tag (InfoTracer)

This PR was merged into the 2.7 branch. Discussion ---------- adding closing tag adding the closing tag of the img element in the example code Commits ------- 88d59cf adding closing tag

Author: xabbuh

cookbook/email/email.rst

@@ -136,7 +136,7 @@ template might look something like this:
  Thanks!
 
  {# Makes an absolute URL to the /images/logo.png file #}
- <img src="{{ absolute_url(asset('images/logo.png')) }}"
+ <img src="{{ absolute_url(asset('images/logo.png')) }}">
 
 .. versionadded:: 2.7
  The ``absolute_url()`` function was introduced in Symfony 2.7. Prior