CI: Pin syn to 2.0.32

[danielabrozzoni]

No description provided.

[apoelstra]

I'm a little surprised that any syn 2.0.x works with 1.48.

The point of the existing serde pins is to keep syn at 1.x. I wonder if it would be possible to remove or relax those now?

[apoelstra]

My approach to this CI failure would be to look at whatever's depending on syn 2.x and downgrade that.

[apoelstra]

On second thought, I don't care enough about the detailed reasons for serde deps to be breaking our shit. We should drop serde_derive which should eliminate all the proc-macro nastiness and move on. Which is a bigger project and independent of this PR.

[apoelstra]

ACK 3d5cf3b

[yancyribbens]

@danielabrozzoni thanks for fixing this! I looked into fixing this but I didn't think to try syn 2.0.x. How did you decide which version of syn to use?

[danielabrozzoni]

@yancyribbens in this case I think I just looked at the compiler error and downgrade the syn dependency until it compiled. Generally, I think using cargo tree with the latest toolchain and using the output to figure out which of our dependencies is importing the broken dependency and pinning that is a better approach, as Andrew suggested above.