Removed bad DNSBL providers.

see #1496

modoboa/admin/constants.py

@@ -12,7 +12,6 @@ DNSBL_PROVIDERS = [
     "bad.psky.me",
     "bl.deadbeef.com",
     "bl.emailbasura.org",
-    "bl.spamcannibal.org",
     "bl.spamcop.net",
     "blackholes.five-ten-sg.com",
     "blacklist.woody.ch",
@@ -25,7 +24,6 @@ DNSBL_PROVIDERS = [
     "dnsbl-1.uceprotect.net",
     "dnsbl-2.uceprotect.net",
     "dnsbl-3.uceprotect.net",
-    "dnsbl.cyberlogic.net",
     "dnsbl.inps.de",
     "dnsbl.sorbs.net",
     "drone.abuse.ch",