Remove traces of nameservers ns-aws, ns-azure

- ns-aws & ns-azure have been replaced by ns-hetzner & ns-ovh
- ns-azure has been completely destroyed (`terraform apply -destroy`);
  the elastic IP has been released, so there's no hope of bringing it
  back.
- ns-aws has been renamed to "blocked.sslip.io". It no longer answers
  DNS queries, but lives on as the website we point "blocked" queries to
  that warns about phishing.
- Some of the Markdown files' changes were mere reformatting changes

integration_speed_test.go

@@ -63,7 +63,7 @@ var _ = Describe("speed", func() {
 			// The queries/second is conservative, realistically should be higher
 			// - queries are done sequentially, not in parallel
 			// - each query includes an overhead of 4 Expect()
-			// current max queries is 132/second (ns-aws.sslip.io.)
+			// current max queries is 2047/second (ns-ovh.sslip.io.)
 			// ~19k Apple M2
 			// ~8k vSphere Xeon D-1736 2.7GHz
 			// ~6k AWS Graviton T2