Assuming that redacted URL that you included in your query has asterisks (*) whereever you are placing an ID, it looks like you might be missing the contact ID that you want to remove. The endpoint takes 2 IDs - the company ID and the Contact ID.
So, an example URL would look like: https://api.hubapi.com/companies/v2/companies/39238082/contacts/270146?hapikey=demo
The first ID is the company ID and the second is the contact id. Also, be sure that you're including a content-type: application/json in your request headers.