patch: include `shuffles` in transcript, even when empty

[guorong009]

Description

• Add the shuffles to PinnedConstraintSystem::fmt, even when empty

Related issues

• Resolve #227 (Originated from #195)

Changes

• remove the empty check condition of shuffles in PinnedConstraintSystem::fmt
• update the plonk_api test

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 81.89%. Comparing base (b4d1c4c) to head (2e6a7d6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #348 +/- ## ========================================== - Coverage 81.89% 81.89% -0.01% ========================================== Files 82 82 Lines 17010 17008 -2 ========================================== - Hits 13930 13928 -2 Misses 3080 3080 ```

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[ed255]

As a reminder, in the latest release we had vk version 0x03: https://github.com/privacy-scaling-explorations/halo2/blob/73408a140737d8336490452193b21f5a7a94e7de/halo2_proofs/src/plonk.rs#L64 Currently in main (not yet released) we have version 0x04: https://github.com/privacy-scaling-explorations/halo2/blob/b4d1c4c9c2cd4fdeab2b66b6872cdabbf700fcc9/halo2_backend/src/plonk.rs#L58

So there's no need to bump the vk version and we can use 0x04 for the next release.