identify: consider dropping the protocol version

[p-shahi]

Go through old kubo and libp2p versions that implemented the identify protocol versions, cross reference in probelabs to see which are still in use, and see if we can drop the /ipfs/0.1.0 protocol version altogether

[mxinden]

For what it is worth, I can not find a version of rust-libp2p that ever supported /ipfs/0.1.0. Already since libp2p/rust-libp2p#116 rust-libp2p uses /ipfs/id/1.0.0.

[marten-seemann]

This was dropped in #461, almost 5 years ago. This should be safe to remove now.

[marten-seemann]

@achingbrain Would this change break compatibility with js-libp2p versions?

[achingbrain]

It should be fine - js-libp2p only uses the protocol version field as peer metadata and doesn't act on it