fix: remove t_open_air_rooved from s_garage_roof_1

[0Monet]

Checklist

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

Remove t_open_air_rooved from s_garage_roof_1 because t_open_air_rooved places flat roof on level 2

Describe the solution

Delete t_open_air_rooved and its symbol from the mapgen s_garage_roof_1

Describe alternatives you've considered

Use t_open_air_rooved_outside but this terrain, like t_open_air_rooved, places a flat roof on the level above.

Additional context

Before:

After: