Rename pep8 to pycodestyle.

[ericsnowcurrently]

(copied from PR #6570)

For #410

Not 100% sure if this passes CI checks (my computer was a bit finicky with unit tests), but I am setting up the PR now to trigger the CI system and see if everything looks good.

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Has a news entry file (remember to thank yourself!)
• Appropriate comments and documentation strings in the code
• Has sufficient logging.
• Has telemetry for enhancements.
• Unit tests & system/integration tests are added/updated
• Test plan is updated as appropriate
• package-lock.json has been regenerated by running npm install (if dependencies have changed)
• The wiki is updated with any design decisions/details.

[codecov-io]

Codecov Report

Merging #7134 into master will decrease coverage by 0.73%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #7134      +/-   ##
==========================================
- Coverage   58.48%   57.74%   -0.74%     
==========================================
  Files         485      485              
  Lines       21437    21098     -339     
  Branches     3462     3457       -5     
==========================================
- Hits        12537    12184     -353     
- Misses       8122     8138      +16     
+ Partials      778      776       -2

Impacted Files	Coverage Δ
src/client/linters/constants.ts	100% <ø> (ø)	⬆️
src/client/linters/types.ts	100% <ø> (ø)	⬆️
src/client/linters/pycodestyle.ts	100% <100%> (ø)
src/client/linters/linterManager.ts	72.6% <100%> (ø)	⬆️
src/client/common/installer/productNames.ts	100% <100%> (ø)	⬆️
src/client/common/configSettings.ts	57.54% <100%> (ø)	⬆️
src/client/common/installer/productInstaller.ts	77.24% <100%> (ø)	⬆️
src/client/testing/common/updateTestSettings.ts	96.42% <100%> (+0.68%)	⬆️
src/client/common/installer/productService.ts	100% <100%> (ø)	⬆️
src/client/common/types.ts	100% <100%> (ø)	⬆️
... and 34 more

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