manpage: fix minor styling issue
manpage: fix minor styling issue

Remove bold formatting from the characters which should only
help to express the enumeration of different sub-commands.

Signed-off-by: Michael Heimpold <59934addbc17c0fa64a0bf4bb38537fc23439974@heimpold.de>

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