git Actions use `ubuntu-22.04` instead of deprecated `ubuntu-18.04` for PR conflicts checker
```
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1 error and 1 warning
Check PR status: conflicts and resolution
This request was automatically failed because there were no enabled runners online to process the request for more than 1 days.
PR Conflicts checker: .github#L1
The ubuntu-18.04 environment is deprecated, consider switching to ubuntu-20.04(ubuntu-latest), or ubuntu-22.04 instead. For more details see https://github.com/actions/virtual-environments/issues/6002
```