fix: lgeacy library block child.save fails in production instance while migrating (#37573)

The child.save() call while migrating legacy library block to library version 2 fails with `InvalidScopeError` due to presence of `LmsFieldData` in` _bound_field_data` field. Removing this call does not seem to have any adverse affect.

xmodule/library_content_block.py

@@ -325,7 +325,6 @@ class LegacyLibraryContentBlock(ItemBankMixin, XModuleToXBlockMixin, XBlock):
                 # Since after migration, the component in library is in draft state, we want to make sure that sync icon
                 # appears when it is published
                 child.upstream_version = 0
-                child.save()
                 # Use `modulestore()` instead of `self.runtime.modulestore` to make sure that the XBLOCK_UPDATED signal
                 # is triggered
                 store.update_item(child, None)