mkosi: move config options

mkosi: move config options

Move some config option in the right section, fixes the following warning:
```
mkosi.conf: Setting Credentials should be configured in [Runtime], not [Host].
mkosi.conf: Setting RuntimeBuildSources should be configured in [Runtime], not [Host].
mkosi.conf: Setting RuntimeScratch should be configured in [Runtime], not [Host].
mkosi.conf: Setting QemuSmp should be configured in [Runtime], not [Host].
mkosi.conf: Setting QemuSwtpm should be configured in [Runtime], not [Host].
mkosi.conf: Setting QemuVsock should be configured in [Runtime], not [Host].
mkosi.conf: Setting QemuKvm should be configured in [Runtime], not [Host].
```