curl --request DELETE \
  --url https://api.lemlist.com/api/campaigns/{campaignId}/leads/{email} \
  --header 'Authorization: Basic <encoded-value>'

{
  "email": "alex.doe@example.com",
  "_id": "lea_8RmJYElD9S5Jp2kyv",
  "isPaused": false,
  "campaignId": "cam_8qJ1qAE5tekBYkJac",
  "contactId": "ctc_joap8q9YGlV45Ypc6"
}