docs/scenarios: remove bootname for rescue slot in additinal rescue slot
docs/scenarios: remove bootname for rescue slot in additinal rescue slot

Avoid having bootname defined for the rescue slot, as it when updated
would result in RAUC would overwrite bootorder to prefer the rescue slot.

Signed-off-by: Sean Nyekjaer <4b16f768201d1f7aa2c0e564fab375968fb60082@siemensgamesa.com>

jluebbe/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,rauc/rauc