fix: add org_id attribute to provider configuration

[patst]

Description of your changes

Fixes #23

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Built it locally and created a folder with this providerconfig secret:

{
  "auth": "admin:superSecret",
  "url": "https://<mygrafanaurl>/",
  "org_id": "8"
}

Before the change the folder was always created in the main org. After my change it is created in the org with id 8.

[CLAassistant]

All committers have signed the CLA.

[julienduchesne]

org_id will be deprecated as a provider-level option eventually but it doesn't hurt to add it in the meantime