Use r-universe image while r-4.6 is in alpha/beta

Author: jeroen

Dockerfile

@@ -1,5 +1,5 @@
 # TODO: switch to release container when R-4.6 is out
-FROM ghcr.io/r-devel/ubuntu-devel
+FROM ghcr.io/r-universe-org/base-image:devel
 
 RUN echo "R_PLATFORM_PKGTYPE=linux.binary.noble-$(arch)" >> "$HOME/.Renviron"