Fix MUSIC_DIRECTORY_SERVE_PATH example value in configuration.rst

Status Name Job ID Coverage
  Lint
passed black #4127

00:00:38

passed flake8 #4128

00:00:30

 
  Test
passed test_api #4129
docker

00:03:16

passed test_front #4227
docker

00:02:19

failed test_front #4222
docker

00:05:04

failed test_front #4130
docker

00:03:45