Drop Python 3.8 support

[sir-sigurd]

Description

TODO

• [x] Changelog entry (skip if change is not significant to end users, e.g. docs only)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 36.68%. Comparing base (cdb6fe4) to head (8a8fd27).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3993 +/- ## ======================================= Coverage 36.68% 36.68% ======================================= Files 724 724 Lines 32254 32254 Branches 4773 4773 ======================================= Hits 11833 11833 Misses 19758 19758 Partials 663 663 ``` | [Flag](https://app.codecov.io/gh/quiltdata/quilt/pull/3993/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | Coverage Δ | | |---|---|---| | [api-python](https://app.codecov.io/gh/quiltdata/quilt/pull/3993/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | `90.95% <ø> (ø)` | | | [catalog](https://app.codecov.io/gh/quiltdata/quilt/pull/3993/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | `10.70% <ø> (ø)` | | | [lambda](https://app.codecov.io/gh/quiltdata/quilt/pull/3993/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | `87.96% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata#carryforward-flags-in-the-pull-request-comment) to find out more.

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