docs: Correct PJSIP identify endpoint reference in outbound registration example

[cletheren]

In the 'Configuring-Outbound-Registrations.md' page there is a configuration example which includes an endpoint and an identify. In the example, the identify refers to an endpoint with a different name:

[my_provider_endpoint]
type = endpoint

[my_provider_identify]
type = identify
match = <ip address of provider>
endpoint = my_provider      <<<<<<<< should be 'my_provider_endpoint'

The endpoint parameter should reference my_provider_endpoint to match the defined endpoint section.

Changes

• Corrected the endpoint reference in the configuration example.
• Updated two occurrences of the incorrect endpoint name.
• No other changes.