Make sure regen-cases are in regen-all

[sobolevn]

regen-cases introduced in #98830 currently does not check if cases are correctly regenerate in our CI.

See:

cpython/.github/workflows/build.yml

Lines 89 to 100 in e9ac890

	- name: Build CPython
	run: |
	# Deepfreeze will usually cause global objects to be added or removed,
	# so we run it before regen-global-objects gets rum (in regen-all).
	make regen-deepfreeze
	make -j4 regen-all
	make regen-stdlib-module-names
	- name: Check for changes
	run: |
	git add -u
	changes=$(git status --porcelain)
	# Check for changes in regenerated files

Sorry, I was not quick enough to submit this in review :)
PR is on its way.

• PR: gh-99048: add regen-cases to regen-all in Makefile #99049