Remove texinfo dependency from docker and CI configs

We don't need texinfo to build the docs any more, so we can
drop that dependency from our docker and other CI configs.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Changes v4->v5: remove texinfo from ubuntu2004.docker too
7 files changed