Update links in docs to HTTPS when available

[johnpgreen]

There are URLs in the code docs which use HTTP when HTTPS is available for those domains.

Previously: #40732, #36993, #37622

Patch incoming.

[netweb]

Thanks @johnpgreen, could you update the Nginx link in the patch please

It looks like they've changed the anchors in that original page so the new link should be:
https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/#missing-disappearing-http-headers

[johnpgreen]

Updated patch added.

[netweb]

Thanks @johnpgreen :+1

[SergeyBiryukov]

In 41189:

Docs: Replace HTTP links to stackoverflow.com in DocBlocks with HTTPS.

Update the Nginx "Missing (disappearing) HTTP Headers" link.

Props johnpgreen.
Fixes #41331.