Bump MSRV about uom

[iliekturtles]

Copied from #216 before I caught up with this issue:

I'm interested in bumping the MSRV but I'm a bit hesitant to go all the way to 1.60 when the work-arounds to resolve #216 issue aren't too painful and allow for an older MSRV. I don't have a specific policy about when to update the MSRV and what version to jump to so I'm interested in hearing thoughts about going all the way to 1.60.

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After (mostly) reading the Crossbeam thread and now that I've seen the defmt PR I'm more inclined to jump to 1.60. It is ~6 months old if the defmt feature gets accepted alongside serde why deal with feature name work-arounds for both.

Whatever MSRV we jump to I would like to release the current master as v0.34.0 now. Finally get @crystal-growth's remaining quantity/unit PRs merged into a branch to be released as v0.34.1 and allow for changes that need the new MSRV to start being merged into master.

[therealfrauholle]

Possible duplicate of #239 I just saw.

[iliekturtles]

https://github.com/iliekturtles/uom/actions/runs/5365520967/jobs/9734386156?pr=421#step:4:53

log has a MSRV of 1.60.0. I'm looking at this now to fix all the bitrot with the github action failures.