Deprecated commands from gftools

[chris-fj]

As per googlefonts/gftools#501, there are command deprecations that ended up in straight deletion of some subcommands used by the latest version of the build.sh and build-GF.sh scripts. Namely, the fix-dsig and fix-vf-meta. These subcommands are deleted as per gftools==0.9.26 which is the version that pip downloaded when I tried this. Instead of resorting to an old version, I think the script must be updated to reflect these changes.

Thank you for creating this awesome font.