Remove BuildRoot definition

None of currently supported distributions need that.
It was needed last for EL5 which is EOL now

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

nss-mdns.spec

@@ -6,7 +6,6 @@ License: LGPLv2+
 URL: http://0pointer.de/lennart/projects/nss-mdns/
 Group: System Environment/Libraries
 Source: http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-%{version}.tar.gz
-BuildRoot: %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 Requires: avahi
  
 %description