[3.10] bpo-45235: Revert an argparse bugfix that caused a regression (GH-29525)

[miss-islington]

• Revert "bpo-45235: Fix argparse overrides namespace with subparser defaults (bpo-45235: Fix argparse overrides namespace with subparser defaults #28420) ([3.9] bpo-45235: Fix argparse overrides namespace with subparser defaults (GH-28420) #28443)"

This reverts commit a18d522.
(cherry picked from commit 807f839)

Co-authored-by: Raymond Hettinger [email protected]

https://bugs.python.org/issue45235

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[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @rhettinger for commit dd684cb 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

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@rhettinger: Status check is done, and it's a failure ❌ .

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@rhettinger: Status check is done, and it's a failure ❌ .

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@rhettinger: Status check is done, and it's a failure ❌ .

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@rhettinger: Status check is done, and it's a failure ❌ .