Remove %clean section

None of currently supported distributions need that.
Last one was EL5 which is EOL for a while.

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

libgeotiff.spec

@@ -84,9 +84,6 @@ install -p -m 644 %{name}.pc %{buildroot}%{_libdir}/pkgconfig/
 rm -fv %{buildroot}%{_libdir}/lib*.la
 echo  >> %{buildroot}%{_datadir}/epsg_csv/codes.csv
 
-%clean
-rm -rf %{buildroot}
-
 %post -p /sbin/ldconfig
 %postun -p /sbin/ldconfig