replace unicode nonbreaking space with ascii space (#794)

lib/App/Netdisco/Worker/Plugin/Discover.pm

@@ -16,7 +16,7 @@ register_worker({ phase => 'check' }, sub {
   return Status->error("discover failed: no device param (need -d ?)")
     if $device->ip eq '0.0.0.0';
 
-  # runner has already called get_device to promote $job->device
+  # runner has already called get_device to promote $job->device
   return $job->cancel("fresh discover cancelled: $device already known")
     if $device->in_storage
        and ($job->subaction eq 'with-nodes' and not $job->username);