nongnu: steam: Use manifest for propagated inputs.
- nongnu/packages/steam-client.scm (steam)[propagated-inputs]: Remove.
[arguments]: Add former propagated-inputs to manifest.scm and fix
quoting in store-item->manifest-entry output.
I noticed that Steam's propagated-inputs aren't installed into the container environment when Steam is included through store-item->manifest-entry.
Currently we only used propagated-inputs for fonts. Most games seem to still find fonts, but a few don't.
So this fix specifies the fonts in the container manifest instead.