subprojects: the dependency name is now babl-0.1.

This was recently changed in babl, so we need to change the wrap file for builds using subprojects.

I think this is the issue.

See:

• https://github.com/mesonbuild/meson/discussions/10484
• https://mesonbuild.com/Wrap-dependency-system-manual.html#provide-section

Let's try and merge after CI succeeds.