Fluid Sim: Removed unused PointCache pointer

The only uses were setting it to NULL and asserting it is NULL.

source/blender/modifiers/intern/MOD_fluidsim_util.c

@@ -160,10 +160,6 @@ void fluidsim_free(FluidsimModifierData *fluidmd)
 		MEM_SAFE_FREE(fluidmd->fss);
 	}
 
-	/* Seems to never be used, but for sqke of consistency... */
-	BLI_assert(fluidmd->point_cache == NULL);
-	fluidmd->point_cache = NULL;
-
 	return;
 }