CI: Upgrade codecov-action from v3 to v4. #3276

Job	Run time
Lint - Hotkeys & docs sync (lint-hotkeys)	11s
Lint - Commit text format (gitlint)	12s
Lint - Code format (black)	17s
Lint - Docstrings & docs sync (lint-docstring)	19s
Lint - Import order (isort)	14s
Lint - Type consistency (mypy)	35s
Lint - PEP8 & more (ruff)	15s
Lint - Spellcheck (codespell, typos)	19s
Install & test - CPython 3.7 (ubuntu), codecov	59s
Ensure isolated PR commits	1m 14s
Install & test - CPython 3.8 (ubuntu)	59s
Install & test - CPython 3.9 (ubuntu)	54s
Install & test - CPython 3.10 (ubuntu)	58s
Install & test - CPython 3.11 (ubuntu)	58s
Install & test - PyPy 3.7 (ubuntu)	2m 36s
Install & test - PyPy 3.8 (ubuntu)	2m 55s
Install & test - PyPy 3.9 (ubuntu)	2m 30s
Install & test - PyPy 3.10 (ubuntu)	2m 29s
Install & test - CPython 3.11 (macos)	1m 19s
	20m 13s

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