changed target framework to net8

[hallvictoria]

Description

Fixes #

---

PR information

• [ ] The title of the PR is clear and informative.
• [ ] There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• [ ] If applicable, the PR references the bug/issue that it fixes in the description.
• [ ] New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• [ ] I have read the contribution guidelines.

[codecov-commenter]

Codecov Report

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

Project coverage is 85.23%. Comparing base (4c8fb7b) to head (e239f23).

:exclamation: Current head e239f23 differs from pull request most recent head d40351e. Consider uploading reports for the commit d40351e to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #1459 +/- ## ========================================== + Coverage 85.08% 85.23% +0.15% ========================================== Files 35 35 Lines 1998 1998 Branches 378 378 ========================================== + Hits 1700 1703 +3 + Misses 222 219 -3 Partials 76 76 ``` | [Flag](https://app.codecov.io/gh/Azure/azure-functions-python-worker/pull/1459/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Azure) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/Azure/azure-functions-python-worker/pull/1459/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Azure) | `85.18% <ø> (+0.15%)` | :arrow_up: | 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=Azure#carryforward-flags-in-the-pull-request-comment) to find out more.

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