Fix dev requirements

[cdce8p]

Description

We recently upgraded isort to 5.12.0 without realizing that, similar to flake8, they dropped support for Python 3.7.
The requirements_test_pre_commit.txt file wasn't included in the cache key, thus the old cache was reused without actually installing 5.12.0 into the CI environment.

Pre-commit.ci uses the version from pre-commit-config so that was fine.

This PR also updates the version for flake8 to get in sync to our pre-commit config.

--
Tbh as more and more tools start to drop 3.7, I'm not opposed to doing the same. Maybe after the 2.16.0 release?
Pylint could still be used to lint 3.7 code, only run with Python 3.8.

Failing test from #1992: https://github.com/PyCQA/astroid/actions/runs/4046304756/jobs/6958923838

[codecov]

Codecov Report

Merging #1993 (f4772df) into main (156db06) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1993   +/-   ##
=======================================
  Coverage   92.77%   92.77%           
=======================================
  Files          94       94           
  Lines       10931    10931           
=======================================
  Hits        10141    10141           
  Misses        790      790           

Flag	Coverage Δ
linux	92.53% <ø> (ø)
pypy	88.50% <ø> (ø)
windows	92.37% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[github-actions]

The backport to maintenance/2.13.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-maintenance/2.13.x maintenance/2.13.x
# Navigate to the new working tree
cd .worktrees/backport-maintenance/2.13.x
# Create a new branch
git switch --create backport-1993-to-maintenance/2.13.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 03f3ad95b61cf802f484b2515bf7f3cc8d744435
# Push it to GitHub
git push --set-upstream origin backport-1993-to-maintenance/2.13.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-maintenance/2.13.x

Then, create a pull request where the base branch is maintenance/2.13.x and the compare/head branch is backport-1993-to-maintenance/2.13.x.