Bump ic-stable-structures in /rust/image-classification (#894)

Bumps [ic-stable-structures](https://github.com/dfinity/stable-structures) from 0.6.3 to 0.6.4.
- [Release notes](https://github.com/dfinity/stable-structures/releases)
- [Commits](dfinity/stable-structures@v0.6.3...v0.6.4)

---
updated-dependencies:
- dependency-name: ic-stable-structures
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]