Fix import typo in ray casting grid map test module.

Corrected the import statement in the test file by updating the module's name to `ray_casting_grid_map` for consistency with the source file. This ensures proper functionality of the test suite.

Author: AtsushiSakai

tests/test_raycasting_grid_map.py tests/test_ray_casting_grid_map.pytests/test_raycasting_grid_map.py renamed to tests/test_ray_casting_grid_map.py

@@ -1,5 +1,5 @@
 import conftest  # Add root path to sys.path
-from Mapping.ray_casting_grid_map import raycasting_grid_map as m
+from Mapping.ray_casting_grid_map import ray_casting_grid_map as m
 
 
 def test1():