Remove dependency on ark-relations/std

[mzabaluev]

Description

The dependency on ark-relations/std is entirely unneeded.
Currently it adds some dependency dead weight for us due to pulling an outdated version of tracing-subscriber (arkworks-rs/snark#356).

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[Pratyush]

I think it would be preferable to update the dependency in ark-relations. If you'd like to look into that I can help with that, otherwise we can look into it in a little while.

[mzabaluev]

I think it would be preferable to update the dependency in ark-relations.

Sure, but why not remove useless dependencies from the dependency tree as well? This potentially improves build times for library's consumers, and I can't see any downsides.