From here I got that the easiest way is to look for a singularity.conf file and change the "allow setuid=yes" to "allow setuid=no". That file should be located in your singularity installation dir. If you used spack for the installation, the path would look something like this:
/path/to/spack/opt/spack/linux-scientific7-haswell/gcc-4.8.5/singularity-3.5.2-k2cgya4v4mjzvfay2n4jfmy7wbda5ucq/etc/singularity/singularity.conf