Update a managed credential's username and password

post https://api.linode.com/{apiVersion}/managed/credentials/{credentialId}/update

Updates the username and password for a Managed Credential.

This operation can only be accessed by the unrestricted users of an account.

linode-cli managed credential-update-username-password 9991 \
  --username johndoe \
  --password s3cur3P@ssw0rd

<https://www.linode.com/docs/products/tools/cli/get-started/>

account:read_write

<https://techdocs.akamai.com/linode-api/reference/get-started#oauth>