Yeah probably dynamically generated with one of the packages.
But is it working now ?
If not, try move that file to your home folder:
I think its better to move that file out of there as it contains settings that might conflict with Pi-hole:
sudo mv /etc/dnsmasq.d/SoftAp0 ~
And restart:
sudo service pihole-FTL restart
And check status again:
sudo service pihole-FTL status -l
And run a DNS lookup on a Linux, Windows or Mac client PC:
nslookup pi.hole <PIHOLE_IP_ADDRESS>