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>

pngcrush.spec

@@ -11,7 +11,6 @@ URL:            http://pmt.sourceforge.net/%{name}/
 Source0:        http://downloads.sourceforge.net/pmt/%{name}-%{version}-nolib.tar.xz
 # from Debian sid.
 Source1:        %{name}.sgml
-BuildRoot:      %{_tmppath}/%{name}-%{version}-%{release}-root
 BuildRequires:  libpng-devel, zlib-devel, pkgconfig, docbook-utils
 
 %description