Remove !encoder.is_open assertion

[andyleiserson]

Note: target is v27 branch. This backports a variation of a change in #8373.

As discussed in #8373, the assertion that !encoder.is_open is falsified when CommandEncoder::as_hal_mut has been called, so remove it.

Also adds a changelog entry for 98caa62 and a commit that updates Cargo.lock for the v27.0.2 release.

Testing
Untested here, but there are some related tests added on trunk in #8373.

Squash or Rebase? Rebase

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.