how to delete a bundle in symfony

If this wasn’t installed using a dependency manager – that should be all.

first thing if you have not a dependency manager by which you have not installed a bundle
first it is going to be few steps
1- delete /src/Test/BlogBundle directory
2- remove new bundle from /app/AppKernel.php
3- change /app/config/routing.yml file to remove the bundle routes
4- clear cache (either by deleting cache/{$env} or console cache:clear)