fix: networklist editor memory leak [backport]

[NoelStephensUnity]

This fixes an issue where NetworkList properties could cause a small memory leak if they existing on NetworkBehaviour components placed on an in-scene placed NetworkObject.

fix: #3136

Changelog

• Fixed: Issue where NetworkList properties on in-scene placed NetworkObjects could cause small memory leaks when entering playmode.

Testing and Documentation

• No tests have been added.
• No documentation changes or additions were necessary.