chore: Remove unused imports

Run Ruff without F401 exclusion and remove all unused imports (but
those in __init__.py).

Concerns #34.

tests/data/init_model_from_kwargs_parameters.py

@@ -1,6 +1,5 @@
 """Model and kwargs data mappings for testing."""
 
-from rdfproxy import instantiate_model_from_kwargs
 from tests.data.models import ComplexModel, NestedModel, SimpleModel
 
 

tests/test_get_bindings_from_query_result.py

@@ -2,9 +2,8 @@
 
 from collections.abc import Iterator
 
+from SPARQLWrapper import QueryResult
 import pytest
-
-from SPARQLWrapper import JSON, QueryResult, SPARQLWrapper
 from rdfproxy import get_bindings_from_query_result