GHA: Fix lint cache

[hugovk]

For some reason, when the last PR was merged, the lint failed because of an apparently outdated cache:

Run tox -e lint
lint create: /home/runner/work/pylast/pylast/.tox/lint
lint installdeps: pre-commit
lint installed: appdirs==1.4.3,cfgv==3.1.0,distlib==0.3.0,filelock==3.0.12,identify==1.4.11,nodeenv==1.3.5,pre-commit==2.1.1,PyYAML==5.3,six==1.14.0,toml==0.10.0,virtualenv==20.0.8
lint run-test-pre: PYTHONHASHSEED='3856264503'
lint run-test: commands[0] | pre-commit run --all-files
pyupgrade................................................................Failed
- hook id: pyupgrade
- exit code: 1

Executable `/home/runner/.cache/pre-commit/repoy32i7vy1/py_env-python3.8/bin/python` not found

black....................................................................Failed
- hook id: black
- exit code: 1

Executable `/home/runner/.cache/pre-commit/repo4hkcvbl4/py_env-python3/bin/python` not found

flake8...................................................................Failed
- hook id: flake8
- exit code: 1

Executable `/home/runner/.cache/pre-commit/repo0nx3ym4i/py_env-python3.8/bin/python` not found

seed isort known_third_party.............................................Failed
- hook id: seed-isort-config
- exit code: 1

• https://github.com/pylast/pylast/runs/485929900?check_suite_focus=true

There's no way (yet) to delete caches on GHA, you need to stick a version number in the key instead.

[codecov]

Codecov Report

Merging #322 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #322   +/-   ##
=======================================
  Coverage   93.75%   93.75%           
=======================================
  Files           1        1           
  Lines        1265     1265           
=======================================
  Hits         1186     1186           
  Misses         79       79

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