Apply suggestions from code review

Co-authored-by: Dhruv Nair <[email protected]>

Author: sayakpaul

src/diffusers/hooks/group_offloading.py

@@ -611,7 +611,7 @@ def _apply_group_offloading_block_level(
             current_modules = submodule[i : i + num_blocks_per_group]
             start_idx = i
             end_idx = i + len(current_modules) - 1
-            group_id = f"{name}.{start_idx}_to_{end_idx}"
+            group_id = f"{name}_{i}_{i+len(current_modules)-1}"
             group = ModuleGroup(
                 modules=current_modules,
                 offload_device=offload_device,