Fixes https://github.com/brave/brave-browser/issues/55967
Brave Origin branded builds compile out Brave Rewards
(enable_brave_rewards = !is_brave_origin_branded), but the Rewards
keyboard shortcuts were still reported as enabled because
IsCommandDisabledByPolicy only checked kDisabledByPolicy. Gate the
Rewards commands on ENABLE_BRAVE_REWARDS so they are always disabled
when Rewards is not compiled in, mirroring AI Chat, Wallet, Talk, etc.
Brian R. Bondy
2db83a0400