CI: Fix pinning

[tcharding]

MSRV build just broke because of a bunch of dependencies. I did not investigate why I just found a set of versions that builds.

[apoelstra]

Right now the client crate literally does not build for me.

cd client
cargo test

outputs

warning: `bitcoincore-rpc-json` (lib) generated 2 warnings
error[E0599]: the method `to_string` exists for reference `&MessageSignature`, but its trait bounds were not satisfied
   --> client/src/client.rs:880:59
    |
880 |         let args = [address.to_string().into(), signature.to_string().into(), into_json(message)?];
    |                                                           ^^^^^^^^^ method cannot be called on `&MessageSignature` due to unsatisfied trait bounds
    |
   ::: /store/home/apoelstra/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bitcoin-0.31.1/src/sign_message.rs:82:5
    |
82  |     pub struct MessageSignature {
    |     ---------------------------
    |     |
    |     doesn't satisfy `MessageSignature: ToString`
    |     doesn't satisfy `MessageSignature: std::fmt::Display`
    |
    = note: the following trait bounds were not satisfied:
            `MessageSignature: std::fmt::Display`
            which is required by `MessageSignature: ToString`
            `&MessageSignature: std::fmt::Display`
            which is required by `&MessageSignature: ToString`

[tcharding]

Ah bother, so we have a circular problem here, this error you posted is caused by me merging #326 yesterday. And in the time since CI ran on that one (ages ago) the pinning issue arose. So now we have two problems and neither solution can be merged because of the other one ...

[apoelstra]

I think if you fix the first problem in one commit, then this problem in a second commit, that should make everyone happy.

[tcharding]

I think if you fix the first problem in one commit, then this problem in a second commit, that should make everyone happy.

I was just re-writing the PR description to #343 which does exactly that. Please review/merge that one and I'll close this one.

[tcharding]

Closing - now part of #343