[ticket/12989] Remove unused "created_by.jpg"

This image is not used anywhere in prosilver.

PHPBB3-12989
Merge pull request #2884 from Louis7777/develop-ascraeus

[ticket/12989] Remove unused "created_by.jpg"

* Louis7777/develop-ascraeus:
  [ticket/12989] Remove unused "created_by.jpg"