Update act (go-gitea#23512) (go-gitea#23518)

Backport go-gitea#23512.

Update replace:
```diff
- replace github.com/nektos/act => gitea.com/gitea/act v0.234.2-0.20230131074955-e46ede1b1744
+ replace github.com/nektos/act => gitea.com/gitea/act v0.243.1
```

Update require:
```diff
-	github.com/nektos/act v0.0.0
+	github.com/nektos/act v0.2.43
```

Actually, `v0.2.43` doesn't work, it will be replaced by `gitea/act`, so
it's OK to put any version here. But `gitea/act` is based on
`nektos/act`, so keeping the right upstream version will make security
dependabot help.

BTW, the [security
report](https://github.com/go-gitea/gitea/security/dependabot/20) is
false positive, we don't use the artifact server in act, see go-gitea#22738.