Revert "improve shell compatibility of venv activate scripts (#10397)" (#10497)
## Summary
This reverts commit 2f7f9ea571f4fa8d2eefbfa4a95f6bc8fd18175c
(https://github.com/astral-sh/uv/pull/10397). We're seeing some
user-reported failures, so we need to investigate further before
re-shipping.
Re-opens https://github.com/astral-sh/uv/issues/7480.
Closes https://github.com/astral-sh/uv/issues/10487.