fix(rs-port): wrong implemenetation for user data in MetacallFuture

[hulxv]

Description

Please include a summary of the change and which issue is fixed. List any dependencies that are required for this change.

Fixes #(issue_no)

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update
• [ ] Documentation update

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