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>

openpgm.spec

@@ -10,7 +10,6 @@ License:       LGPLv2
 URL:           http://openpgm.googlecode.com/
 Source0:       http://openpgm.googlecode.com/files/libpgm-%{version}~dfsg.tar.gz
 
-BuildRoot:     %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
 
 BuildRequires: python
 BuildRequires: perl-interpreter