Bump to Netty 4.2.6

[VelVeV]

https://netty.io/news/2025/09/08/4-2-6.html

We are happy to announce the release of netty 4.2.6.Final. This is a bug-fix release which fixes a regression introduced by 4.2.5.Final that might affect you if you use BouncyCastle. We decided to do a quick follow-up release here so people that depend on it can still get the fixes for CVE-2025-58057 and CVE-2025-58056 that were part of 4.2.5.Final.

The most important changes are:

BouncyCastleAlpnSslUtils needs to use the correct SSLEngine class as otherwise it will fail to init static fields. (#15630)
IoUring: Allow to create IoHandlerFactory that supports changing the Thread and so supports AutoScalingEventExecutorChooserFactory. (#15608)

[astei]

That update isn't relevant to Velocity, because we don't use BouncyCastle.

Netty 4.2.7 does contain changes relevant to us, so I updated with 13a1c93.