Update all examples of subscribing to static events to include corresponding 'unsubscribing' to that event during termination

[marcemarc]

eg this sort of example:

public class SubscribeToSavedEventComponent : IComponent
{
private readonly ILogger _logger;

    public SubscribeToSavedEventComponent(ILogger logger)
    {
        this._logger = logger;
    }
   
    public void Initialize()
    {
        //specify my event handler
        MemberService.Saved += MemberService_Saved;
    }

    private void MemberService_Saved(IMemberService sender, SaveEventArgs<IMember> e)
    {
        foreach (var member in e.SavedEntities)
        {
            
          //write to the logs every time a member is saved
          this._logger.Info<MyPublishEventComponent>("member {member} has been saved and event fired!", member.Name);
        }
    }
    public void Terminate()
    {
        // Nothing to terminate
    }

should be

public class SubscribeToSavedEventComponent : IComponent
{
private readonly ILogger _logger;

    public SubscribeToSavedEventComponent(ILogger logger)
    {
        this._logger = logger;
    }
   
    public void Initialize()
    {
        //specify my event handler
        MemberService.Saved += MemberService_Saved;
    }

    private void MemberService_Saved(IMemberService sender, SaveEventArgs<IMember> e)
    {
        foreach (var member in e.SavedEntities)
        {
            
          //write to the logs every time a member is saved
          this._logger.Info<MyPublishEventComponent>("member {member} has been saved and event fired!", member.Name);
        }
    }
    public void Terminate()
    {
         //unsubscribe to event during shutdown
        MemberService.Saved -= MemberService_Saved;
    }

See this PR for context: umbraco/Umbraco-CMS#8815

[marcemarc]

PR here: https://github.com/umbraco/UmbracoDocs/pull/2692/files

[nul800sebastiaan]

Fixed in #2692