Don't specify older patchlevel as default R

repo2docker/buildpacks/r.py

@@ -74,7 +74,7 @@ class RBuildPack(PythonBuildPack):
         }
 
         # the default if nothing is specified
-        r_version = "4.1.0"
+        r_version = "4.1"
 
         if not hasattr(self, "_r_version"):
             parts = self.runtime.split("-")