Partially revert 5bb37fb

The {fs} package additionally required modification to vendored `libuv`
source, so r-lib/fs still fails to build.

Reverting to r-wasm/fs@webr for the moment.

inst/webr-remotes

@@ -1,6 +1,6 @@
 r-wasm/LiblineaR@webr
 r-wasm/data.table@webr
-r-lib/fs@main
+r-wasm/fs@webr
 r-wasm/glue@webr
 r-wasm/gt@webr
 r-wasm/htmlwidgets@webr