doc: add a disclamer for the TLS handshake timeouts TL;DR bug in godebug.md

Relates to golang/go#71257. Since post-quantum TLS algorithms are enabled by default, we should warn about the possible bugs with legacy servers (see https://tldr.fail/)

Change-Id: Id5a565c2959c5b0f7b8bdd53ce9e70b191c4bf38
GitHub-Last-Rev: a709e6f
GitHub-Pull-Request: #311
Reviewed-on: https://go-review.googlesource.com/c/website/+/650857
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Roland Shoemaker <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: thomvaill

_content/doc/go1.23.md

@@ -293,6 +293,8 @@ the GODEBUG environment variable.
 The experimental post-quantum key exchange mechanism X25519Kyber768Draft00
 is now enabled by default when [`Config.CurvePreferences`](/pkg/crypto/tls#Config.CurvePreferences) is nil.
 The default can be reverted by adding `tlskyber=0` to the GODEBUG environment variable.
+This can be useful when dealing with buggy TLS servers that do not handle large records correctly,
+causing a timeout during the handshake (see [TLS post-quantum TL;DR fail](https://tldr.fail/)).
 
 Go 1.23 changed the behavior of [`X509KeyPair`](/pkg/crypto/tls#X509KeyPair) and [`LoadX509KeyPair`](/pkg/crypto/tls#LoadX509KeyPair)
 to populate the [`Certificate.Leaf`](/pkg/crypto/tls#Certificate.Leaf) field of the returned [`Certificate`](/pkg/crypto/tls#Certificate).

_content/doc/go1.24.md

@@ -480,6 +480,8 @@ The new post-quantum [`X25519MLKEM768`](/pkg/crypto/tls#X25519MLKEM768) key
 exchange mechanism is now supported and is enabled by default when
 [`Config.CurvePreferences`](/pkg/crypto/tls#Config.CurvePreferences) is nil.
 [GODEBUG setting](/doc/godebug) `tlsmlkem=0` reverts the default.
+This can be useful when dealing with buggy TLS servers that do not handle large records correctly,
+causing a timeout during the handshake (see [TLS post-quantum TL;DR fail](https://tldr.fail/)).
 
 Support for the experimental `X25519Kyber768Draft00` key exchange has been removed.