hie: fix hie.yaml to use default hie-bios script

!13778 accidentally changed hie.yaml to use hie-bios.bat as the
default hie-bios script, which completely breaks hie support on
non-Windows platforms. This patch reverts that change.

hie.yaml

@@ -5,4 +5,4 @@
 # cradle: {bios: {program: "./hadrian/hie-bios.bat"}}
 #
 # The format is documented here - https://github.com/mpickering/hie-bios
-cradle: {bios: {program: "./hadrian/hie-bios.bat"}}
+cradle: {bios: {program: "./hadrian/hie-bios"}}