chore(deps): bump z3 from 0.20.2 to 0.21.0

[dependabot]

Bumps z3 from 0.20.2 to 0.21.0.

Commits

• 1514267 chore: release (#574)
• bbd49f4 chore: Update README.md
• 82c5448 chore: bump z3-sys to use 5.1.0 by default (#585)
• 66f09e9 chore: release z3-src (Z3 z3-5.1.0) (#584)
• 3606767 feat!: auto-detect z3 version (#583)
• 40d92eb feat: Optimize::set_model_handler (#577)
• 385eb26 Don't build xtask tool in wasm cross-compile (#580)
• 70081be fix: add missing inc_ref to ApplyResult's Clone (#578)
• e717cdd chore: bump z3 to use z3-sys 0.12.0 (#575)
• 60eae85 chore(z3-sys): release v0.12.0 (#571)
• Additional commits viewable in compare view

[github-actions]

🔒 HELD — not auto-mergeable (class: zerox-minor). 0.20.2 -> 0.21.0: for a 0.x crate the MINOR is the de-facto major (ordeal 0.9->0.12; object 0.39->0.40 / #938)

Auto-merge has been actively disabled and asserted off by the hold gate (#965). For a 0.x crate the MINOR component is the de-facto major (and for 0.0.x, the patch): ordeal 0.9→0.12 auto-merged as "minor" and hung Test+Z3 for days; object 0.39→0.40 (#938) broke 16 call sites across three unrelated newtype surfaces. Merge this BY HAND only once the FULL suite is green, including the separate --features z3-solver path (required context "Z3 Verification") — the discriminator is CI, not a read of the diff.

[github-actions]

🔒 HELD — not auto-mergeable (class: zerox-minor). 0.20.2 -> 0.21.0: for a 0.x crate the MINOR is the de-facto major (ordeal 0.9->0.12; object 0.39->0.40 / #938)

Auto-merge has been actively disabled and asserted off by the hold gate (#965). For a 0.x crate the MINOR component is the de-facto major (and for 0.0.x, the patch): ordeal 0.9→0.12 auto-merged as "minor" and hung Test+Z3 for days; object 0.39→0.40 (#938) broke 16 call sites across three unrelated newtype surfaces. Merge this BY HAND only once the FULL suite is green, including the separate --features z3-solver path (required context "Z3 Verification") — the discriminator is CI, not a read of the diff.