[Snek] [keith-packard/snek] 43ad46: .github: Switch back to vanilla debian qemu

[Keith Packard]

  Branch: refs/heads/debian-qemu
  Home:   https://github.com/keith-packard/snek
  Commit: 43ad466e0bf0f13959b338c86f2390ba74b7ed09
      https://github.com/keith-packard/snek/commit/43ad466e0bf0f13959b338c86f2390ba74b7ed09
  Author: Keith Packard <keithp at keithp.com>
  Date:   2022-02-12 (Sat, 12 Feb 2022)

  Changed paths:
    M .github/Dockerfile

  Log Message:
  -----------
  .github: Switch back to vanilla debian qemu

Now that qemu supports semihosting on risc-v, we can use the standard
debian version again.

Signed-off-by: Keith Packard <keithp at keithp.com>