fix: change the flat roof in one of the mapgen in the middle of the mansion into indoor open air

[0Monet]

Checklist

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• I wrote the PR title in conventional commit format.
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Purpose of change

Fix because for some reason there is flat roof in the middle of one of the manor's mapgen which seems to be a error as it should be open air.

Describe the solution

Change * to " " since " " is t_open_air_rooved.

Describe alternatives you've considered

none

Additional context

Before:

After: