Update sync command to work in discord.py 2.4

[pythonmcpi]

Rationale

discord.py 2.4 updates the get_translated_payload and to_dict method signatures for application commands, making the CommandTree a required parameter.

Summary of changes made

Support the new function signatures without breaking backwards compatibility with discord.py <= 2.3

Supersedes #230

Checklist

• [x] This PR changes the jishaku module/cog codebase
  • [ ] These changes add new functionality to the module/cog
  • [x] These changes fix an issue or bug in the module/cog
  • [x] I have tested that these changes work on a production bot codebase
  • [x] I have tested these changes against the CI/CD test suite
  • [ ] I have updated the documentation to reflect these changes
• [ ] This PR changes the CI/CD test suite
  • [ ] I have tested my suite changes are well-formed (all tests can be discovered)
  • [ ] These changes adjust existing test cases
  • [ ] These changes add new test cases
• [ ] This PR changes prose (such as the documentation, README or other Markdown/RST documents)
  • [ ] I have proofread my changes for grammar and spelling issues
  • [ ] I have tested that any changes regarding Markdown/RST syntax result in a well formed document

[JDJGInc]

as discord.py version 2.4 released recently this can be merged as confirmed.

[JDJGInc]

and if this gets merged

pr 230 can be closed too.