Try some sql:
Code:
UPDATE Improvements SET TilesRequired = "1" WHERE TilesRequired = "2";
That will automatically update all improvements which provide 0.5 housing per improvement to 1 housing per improvement.
Or, just go to
C:\Program Files (x86)\Steam\steamapps\common\Sid Meier's Civilization VI\Base\Assets\Gameplay\Data\Improvements.xml and do a search for TilesRequired between <Improvements> and </Improvements> and change them all from 2 to 1.