docs: improve Pin.origins example

[lidel]

This updates example in docs to show that multiple multiaddrs of different types can be added:

Thanks @obo20 for noticing this.

[obo20]

one thing that I would mention is that users make sure they're providing the multi address with their public key (as often many addresses are listed when you do ipfs id. This is a small thing though.

[lidel]

Superseded by https://github.com/ipfs/pinning-services-api-spec/pull/72