update demo/oauth2-azure.r to oauth2/v2.0

[klin333]

In the azure demo, it suggests using a legacy endpoint.

httr/demo/oauth2-azure.r

Lines 18 to 24 in df11e21

	# Obtain OAuth2 endpoint settings for azure:
	# This uses the "common" endpoint.
	# To use a tenant url, create an
	# oauth_endpoint(authorize = "https://login.windows.net/<tenant_id>/oauth2/authorize",
	# access = "https://login.windows.net/<tenant_id>/oauth2/token")
	# with <tenant_id> replaced by your endpoint ID.
	azure_endpoint <- oauth_endpoints("azure")

It needs to be updated to the below, as outlined in Microsoft guide https://learn.microsoft.com/en-us/entra/identity-platform/v2-oauth2-auth-code-flow

endpoint <- httr::oauth_endpoint(
  authorize = sprintf("https://login.windows.net/%s/oauth2/v2.0/authorize", tenant_id),  # changed here by adding /v2.0/
  access = sprintf("https://login.windows.net/%s/oauth2/v2.0/token", tenant_id))

In addition httr::oauth_endpoints("azure") gives "https://login.windows.net/common/oauth2/authorize", which is no longer supported since 2018 I believe.

I can confirm this change is required.