net-mgmt/bosun: fix build on riscv64

Bump version of the golang.org/x/net and golang.org/x/sys dependencies
to enable a build on riscv64-freebsd. This requires cascading updates
to the golang.org/x/sync and golang.org/x/crypto dependencies.

Sponsored by: Berliner Linux User Group e.V.
Approved by: portmgr (build fix blanket)