Remove obsolete members

[Jericho]

The following are obsolete:

• The Response property of the StrongGrid.Models.Webhooks.DeferredEvent class
• Twilio SendGrid no longer supports SendGrid for New Relic and the related integration features as of August 30, 2022:
  • NewRelicSettings class
  • StrongGrid.Resources.Settings.GetNewRelicSettingsAsync
  • StrongGrid.Resources.Settings.UpdateNewRelicSettingsAsync
• As of august 2020, SendGrid has retired BCC mail settings:
  • StrongGrid.Resources.Settings.GetBccMailSettingsAsync
  • StrongGrid.Resources.Settings.UpdateBccMailSettingsAsync
• As of august 2020, SendGrid has retired Spam Check mail settings
  • StrongGrid.Resources.Settings.GetSpamCheckMailSettingsAsync
  • StrongGrid.Resources.Settings.UpdateSpamCheckMailSettingsAsync
• Twilio SendGrid will retire Email Monitor on December 13, 2022:
  • StrongGrid.Resources.Subusers.GetMonitorSettingsAsync
  • StrongGrid.Resources.Subusers.CreateMonitorSettingsAsync
  • StrongGrid.Resources.Subusers.UpdateMonitorSettingsAsync
  • StrongGrid.Resources.Subusers.DeleteMonitorSettingsAsync
• StrongGrid.Utilities.SendGridAttachment has been replaced with the Attachment class
• StrongGrid.WebhookParser.ParseInboundEmailWebhook