debian: don't force-create the orig tarball

debian/gbp.conf

@@ -7,7 +7,6 @@ upstream-branch=master
 debian-branch=master
 upstream-tree=branch
 tag=False
-force-create=True
 compression=xz
 compression-level=9ev
 builder=debuild --prepend-path=/usr/lib/ccache -eFS_* -eCCACHE_* -i\.git -I.git -Zxz -z9