fix(spotify): fix wrongly escaped variables in install script

[phts]

Otherwise the original files just got deleted without making a copy:

....
Creating directories
Creating data directory
cp: cannot create regular file '$DAEMON_DATA_PATH/config.yml': No such file or directory
chown: cannot access '$DAEMON_DATA_PATH/config.yml': No such file or directory
cp: cannot create regular file '$DAEMON_DATA_PATH/credentials.json': No such file or directory
chown: cannot access '$DAEMON_DATA_PATH/credentials.json': No such file or directory
Creating Start Script
plugininstallend

and requires reauthorization

cc @devgianlu