remove type: ignore comment statements

wile working on issue #990 many type-checking errors were removed, but some could not be, and in those cases a #type: ignore
statement was added.
Ideally, those should be fixed as well.
Some #type: ignore cannot be removed as they form part of the type-dispatched code.
The places where #type: ignore was added that may e can be fixed come from here:

Pixi task (default): mypy
imod\typing\structured.py:58: error: Argument 1 to "check_sizes" has incompatible type "defaultdict[Hashable, set[int]]"; expected "defaultdict[str, set[int]]"  [arg-type]
imod\typing\structured.py:67: error: Incompatible return value type (got "Coordinates", expected "dict[str, Any]")  [return-value]
imod\typing\structured.py:94: error: Argument 2 to "zip" has incompatible type "tuple[tuple[int, ...], ...] | None"; expected "Iterable[tuple[int, ...]]"  [arg-type]
imod\typing\structured.py:96: error: Argument 1 to "check_sizes" has incompatible type "defaultdict[Hashable, set[tuple[int, ...]]]"; expected "defaultdict[str, set[int]]"  [arg-type]
imod\typing\structured.py:247: error: List comprehension has incompatible type List[DataArray | Dataset]; expected List[DataArray]  [misc]
imod\typing\structured.py:252: error: Argument 1 to "_merge_partitions" has incompatible type "list[DataArray | Dataset]"; expected "list[DataArray]"  [arg-type]
imod\util\spatial.py:233: error: Argument 1 to "drop_vars" of "Dataset" has incompatible type "Hashable | Any"; expected "str | Iterable[Hashable] | Callable[[Dataset], str | Iterable[Hashable]]"  [arg-type]
imod\util\spatial.py:340: error: Item "None" of "Match[str] | None" has no attribute "groups"  [union-attr]
imod\prepare\wells.py:82: error: Value of type "float" is not indexable  [index]
imod\mf6\simulation.py:177: error: Argument 1 to "timestep_duration" has incompatible type "list[datetime64 | Any]"; expected "ndarray[Any, Any]"  [arg-type]
Found 10 errors in 4 files (checked 103 source files)

Start by running the default Pixi task, mypy, and compare its output with the listed errors. Inspect imod/typing/structured.py, imod/util/spatial.py, imod/prepare/wells.py, and imod/mf6/simulation.py at the reported lines. Done means the fixable type errors and their #type: ignore comments are removed, while comments required for type-dispatched code remain.