fix(doc/architecture.md): fix typo — radicle-ci-broker

Signed-off-by: Lars Wirzenius liw@liw.fi

 * The Radicle node (`radicle-node`).
 * The Radicle CI broker (`cib`).
 * An adapter the runs CI, possibly using an external CI service.
 * A management tool (`cibool`).
 * A management tool (`cibtool`).
 ~~~pikchr
 right