fix(state): prevent DeprecationWarning on shard reconnect

[shiftinv]

Summary

Rebinding guild/member references on shard reconnect also updates Message.interaction.user; interaction is deprecated, so this should use the underlying _interaction instead to avoid copious amounts of DeprecationWarnings (one per cached message).

Checklist

• If code changes were made, then they have been tested
  • I have updated the documentation to reflect the changes
  • I have formatted the code properly by running pdm lint
  • I have type-checked the code by running pdm pyright
• This PR fixes an issue
• This PR adds something new (e.g. new method or parameters)
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)