Update mypy requirement from ~=0.971 to ~=0.981 (Pycord-Development#1652

)

Updates the requirements on [mypy](https://github.com/python/mypy) to permit the latest version.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.971...v0.981)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:development
...

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requirements-dev.txt

@@ -3,5 +3,5 @@ pylint~=2.15.2
 pytest~=7.1.3
 pytest-asyncio~=0.19.0
 # pytest-order~=1.0.1
-mypy~=0.971
+mypy~=0.981
 coverage~=6.4