tidy-up: miscellaneous

- sha256: fix backend priority in comment.
- URLs: link to IETF URLs to the HTML document, to match others.
- VERSIONS.md: use unified date format for recent entries too.
  Ref: ce5d32032f
- GHA/labeler.yml: alpha-sort file masks in a label block.
- tests/server/mqttd: fix call arg list in a disabled function.
- tests/server/mqttd: fix comment.

Closes #21473

docs/ECH.md

@@ -135,7 +135,7 @@ LD_LIBRARY_PATH=$HOME/code/openssl ./src/curl -vvv --ech ecl:AED+DQA8yAAgACDRMQo
 
 There is a reason to want this command line option - for use before publishing
 an ECHConfigList in the DNS as per the Internet-draft [A well-known URI for
-publishing ECHConfigList values](https://datatracker.ietf.org/doc/draft-ietf-tls-wkech/).
+publishing ECHConfigList values](https://datatracker.ietf.org/doc/html/draft-ietf-tls-wkech/).
 
 If you do use a wrong ECHConfigList value, then the server might return a
 good value, via the `retry_configs` mechanism. You can see that value in

docs/TODO.md

@@ -791,7 +791,7 @@ done, and thus maintain its connection pool, DNS cache and more.
 
 Consider a command line option that can make curl do multiple serial requests
 while acknowledging server specified [rate
-limits](https://datatracker.ietf.org/doc/draft-ietf-httpapi-ratelimit-headers/).
+limits](https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-ratelimit-headers/).
 
 See [curl issue 5406](https://github.com/curl/curl/issues/5406)
 

docs/VERSIONS.md

@@ -69,12 +69,12 @@ dates. The tool was called `httpget` before 2.0, `urlget` before 4.0 then
 same version numbers.
 
 - 8.21.0: pending
-- 8.20.0: April 29, 2026
-- 8.19.0: March 11, 2026
-- 8.18.0: January 7, 2026
-- 8.17.0: November 5, 2025
-- 8.16.0: September 10, 2025
-- 8.15.0: July 16, 2025
+- 8.20.0: April 29 2026
+- 8.19.0: March 11 2026
+- 8.18.0: January 7 2026
+- 8.17.0: November 5 2025
+- 8.16.0: September 10 2025
+- 8.15.0: July 16 2025
 - 8.14.1: June 4 2025
 - 8.14.0: May 28 2025
 - 8.13.0: April 2 2025