refactor(graph): remove dead code in extract_package_subset

Remove redundant ROOT node inclusion check in extract_package_subset function.
The _collect_dependents function already handles ROOT inclusion automatically
when traversing parent dependencies, making the explicit check unnecessary.

This removes 7 lines of dead code while maintaining the same functionality.
All tests continue to pass and ROOT is still properly included in subsets
when target packages are top-level dependencies.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: dhellmann

src/fromager/commands/graph.py

@@ -552,13 +552,6 @@ def extract_package_subset(
     for target_node in target_nodes:
         _collect_dependencies(target_node, related_nodes, visited_down)
 
-    # Always include ROOT if any target nodes are top-level dependencies
-    for target_node in target_nodes:
-        for parent_edge in target_node.parents:
-            if parent_edge.destination_node.key == ROOT:
-                related_nodes.add(ROOT)
-                break
-
     # Create new graph with only related nodes
     subset_graph = DependencyGraph()
     _build_subset_graph(graph, subset_graph, related_nodes)