Check that an Interval is an interval

As suggested in the to-do [here](https://github.com/aclai-lab/SoleLogics.jl/blob/d92b61a4f8dc37d3482362e567cf6e653f39755b/src/utils/frames/worlds/geometrical-worlds.jl#L131-L132), I suggest to check that an object of type Interval is, indeed, and interval, not only for debugging, i.e., x

The issue points directly to `src/utils/frames/worlds/geometrical-worlds.jl` (lines 131-132). Start by opening that file at the referenced lines to see the current interval check path and the exact comment/code to remove. Apply the suggested edit in that one spot, then run the project tests (or the relevant module tests if you can locate them) to confirm no regressions and that the interval check logic is now aligned with the intended invariant.

Written by the indexing model from the issue text.