Update TagRepository.php

The column name was missing in the group by.

I got this error :

<code>
An exception occurred while executing 'SELECT c0_.name AS name0, COUNT(c1_.tag_id) AS sclr1 FROM Community c0_ INNER JOIN CommunitySubscribing c1_ ON c0_.id = c1_.tag_id WHERE c1_.resource_type = ? GROUP BY c1_.tag_id ORDER BY sclr1 DESC' with params ["theme"]:

SQLSTATE[42803]: Grouping error: 7 ERREUR: la colonne « c0_.name » doit apparaître dans la clause GROUP BY ou doit être utilisé dans une fonction d'agrégat
LINE 1: SELECT c0_.name AS name0, COUNT(c1_.tag_id) AS sclr1 FROM Co...
</code>

My modification fix this problem.