ci: do not install pandoc and move to container infrastructure
ci: do not install pandoc and move to container infrastructure

pandoc is not really needed in order to perform testing, so we
don't bother with installation.  Tests tend to run faster on
the new infrastructure.

Signed-off-by: Paul Osborne <b6afffd6c1a00645fdd04b09edf63d034a949a39@gmail.com>

posborne/cmsis-svd,flit/cmsis-svd