fix: use dimension type from constructor instead of calling getDimension

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We ran into a mod compat issue from a mod overriding getDimension in its own World subclass and returning a value from a field it initialized in the subclass constructor. Since Lithium's inject runs before the subclass constructor, this caused an NPE.

The best solution IMO is to just use the dimension type provided as the constructor argument, rather than retrieving it through getDimension. This changes nothing for vanilla behavior because the default implementation of World#getDimension() returns a field initialized by that argument.