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 Currently it adds some dependency dead weight for us due to pulling an outdated version of tracing-subscriber (https://github.com/arkworks-rs/snark/issues/356).

---

Before we can merge this PR, please make sure that all the following items have been checked off. If any of the checklist items are not applicable, please leave them but write a little note why.

• [x] Targeted PR against correct branch (master)
• [x] Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• [ ] Wrote unit tests
• [ ] Updated relevant documentation in the code
• [x] Added a relevant changelog entry to the Pending section in CHANGELOG.md
• [ ] Re-reviewed Files changed in the Github PR explorer

[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.