Backport #29788 by @wolfogre
I was trying to run unit tests for Gitea on act runner, by using `make
test`.
It failed with log:
```
2024/03/14 03:09:26 ...s/setting/setting.go:180:loadRunModeFrom() [F] Gitea is not supposed to be run as root. Sorry. If you need to use privileged TCP ports please instead use setcap and the `cap_net_bind_service` permission
```
So it will be convenient to skip by setting environment, since it's OK
to use root user in job containers.
It's not a bug, but I want to backport it to v1.21 since it doesn't
break anything.
---------
Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
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