Bump Noir from `v1.0.0-beta.14` to `v1.0.0-beta.20`

[krushimir]

The extractor pins Noir at rev 9a5b3695b (1.0.0-beta.12). Libraries in the Noir ecosystem now target >=1.0.0, causing extraction failures on noir-bignum v0.9.2:

• No method named 'as_vector' - API added after beta.12
• Integers must have the same bit width - stricter type checking rejects valid u128 operations, producing HirStatement::Error that causes the extractor to panic at generator.rs:1405

The extractor should also handle HirStatement::Error gracefully (skip with a warning) as a defensive measure for future version mismatches.

[iamrecursion]

Is this addressed by #247?

[iamrecursion]

When we bump further, make sure to check for features that have stabilised in the time between beta versions! It looks like we missed the stabilisation of associated constants (filed as #272) at some point, for example.

[iamrecursion]

The latest beta is v1.0.0-beta.20 so we should get up to date with that sooner rather than later!