Fix: classroom assignment schema fields

[yanyongyu]

fix #144

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 17.82%. Comparing base (270b57c) to head (e7c1c9e). Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...kit/versions/ghec_v2022_11_28/models/group_0025.py	0.00%	3 Missing :warning:
...bkit/versions/ghec_v2022_11_28/types/group_0025.py	0.00%	3 Missing :warning:
...ithubkit/versions/v2022_11_28/models/group_0025.py	0.00%	3 Missing :warning:
githubkit/versions/v2022_11_28/types/group_0025.py	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #146 +/- ## ======================================= Coverage 17.82% 17.82% ======================================= Files 4842 4842 Lines 223460 223460 ======================================= Hits 39838 39838 Misses 183622 183622 ``` | [Flag](https://app.codecov.io/gh/yanyongyu/githubkit/pull/146/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ju4tCode) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/yanyongyu/githubkit/pull/146/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ju4tCode) | `17.82% <0.00%> (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=Ju4tCode#carryforward-flags-in-the-pull-request-comment) to find out more.

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