Use environment variable instead of fixed url in code

[Sandro-Meireles]

The following lines use a fixed URL instead environment variable. There is already a variable that has the same value WHATSAPP_API_URL

weni-integrations-engine/marketplace/wpp_templates/requests.py

Line 19 in bd0702d

response = requests.get(url=f"https://graph.facebook.com/v14.0/{waba_id}/message_templates", params=params)

weni-integrations-engine/marketplace/wpp_templates/requests.py

Line 27 in bd0702d

response = requests.get(url=f"https://graph.facebook.com/v14.0/{waba_id}", params=params)

weni-integrations-engine/marketplace/wpp_templates/requests.py

Line 38 in bd0702d

response = requests.post(url=f"https://graph.facebook.com/v14.0/{waba_id}/message_templates", params=params)

weni-integrations-engine/marketplace/wpp_templates/requests.py

Line 46 in bd0702d

return requests.delete(url=f"https://graph.facebook.com/v14.0/{waba_id}/message_templates", params=params)

In addition, it would be more interesting to use a method that returns the URL from the endpoint to avoid rework, like: https://github.com/weni-ai/weni-integrations-engine/pull/207/files#diff-1be15eeb5dbb3513b189266691c6b4af6e9c40df745b24f0b2a5d17e844cfeedR28

[matmsa27]

This PR #233 fixed and change the code to use the environment variable.