Revert change of path type

The change caused lots of evaluation errors, since it caused derivations to no longer be valid paths as well.

Changed files
+1 -2
lib
+1 -2
lib/types.nix
···
path = mkOptionType {
name = "path";
# Hacky: there is no ‘isPath’ primop.
-
# need to check isString first because otherwise toString throws an error.
-
check = x: builtins.isString x && builtins.substring 0 1 (toString x) == "/";
+
check = x: builtins.substring 0 1 (toString x) == "/";
merge = mergeOneOption;
};