replace pkg_resources with importlib.metadata

[StarrFox]

Rationale

setuptools (pkg_resources) is no longer installed in venvs by default starting in 3.12 as per python/cpython#95299

so code using it doesn't work anymore

Summary of changes made

I replaced the usages of pkg_resources with importlib.metadata

before in meta.py there was some code that removed the jishaku module from it's internal cache; this is no longer needed when using importlib.metadata

another solution to this might be to add setuptools to jishaku's dependencies

Checklist

• This PR changes the jishaku module/cog codebase
  • These changes add new functionality to the module/cog
  • These changes fix an issue or bug in the module/cog
  • I have tested that these changes work on a production bot codebase
  • 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