fix: remove dead links from the readme

The tech docs template's own documentation has been missing since
GOV.UK decommissioned GOV.UK PaaS in 2023.

See alphagov/tdt-documentation#210

README.md

@@ -37,13 +37,5 @@ This website is hosted on [GitHub Pages](https://pages.github.com/).
 
 ## Configuring the website
 
-### Global configuration
-
-The [GOV.UK Tech Docs Template global configuration options](https://tdt-documentation.london.cloudapps.digital/configure_project/global_configuration/)
+The [GOV.UK Tech Docs Template global configuration options](https://github.com/alphagov/tech-docs-template/blob/main/optional/config/tech-docs.yml.tt)
 can be used in this repository to configure the Cloud Platform user guide.
-
-### Structuring documentation and page configuration
-
-The [GOV.UK Tech Docs Template "Configure your documentation project"](https://tdt-documentation.london.cloudapps.digital/configure_project/)
-offers a range of guidance regarding configuration options to help structure
-documentation and configure pages separately.