chore: remove failing tests

[ivokub]

Description

GKR serialization test makes sense, but it creates an issue as every time we create a new release it seems to start failing. As such, imo it is not reliable. And it also doesn't make sense to commit 10MB test fixture every time we do a release. As the file is binary then it just wastes space.

I also removed a multicommit test for case when we call WithCommitment without any inputs. For Groth16 backend it made sense, as the commitments were randomized, but with PLONK the commitment is deterministic (it is KZG commitment of the variables committed to).

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Note

Low Risk
Changes only remove test generation and tests; no production proving, commitment, or GKR runtime logic is modified.

Overview
Removes the GKR-Poseidon2 end-to-end serialization integration path: the test vector generator no longer compiles a BLS12-377 circuit or writes gkr_poseidon2.scs / .wtns under integration_test/, and the integration test that loaded those binaries and called Solve is deleted. The generator’s parallel task list is trimmed accordingly, and the goroutine loop now passes each task into the closure and panics on error inline (replacing assertNoError).

Also deletes TestNoCommitVariable in std/multicommit, which asserted that a circuit could succeed when WithCommitment ran without using the commitment—behavior that matched Groth16-style randomization but not PLONK’s deterministic KZG commitments.

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