conversations.declineSharedInvite method
Usage info
This Slack Connect API method declines (i.e., doesn't approve) an accepted invitation to a Slack Connect channel.
If you'd like to approve an accepted invitation, use the conversations.approveSharedInvite method.
You'll likely want to subscribe to the shared_channel_invite_accepted event in order to keep track of the invitations that have been accepted and are waiting for approval.