Document new signing key D91A82DB3CD36409 in RELEASE.md

[toby-bro]

Description

Hello,
It seems that the release 1.9.2 is signed with a new PGP key that is not documented in the RELEASE.md file.

• The RELEASE.md only documents the old key: 5B482B8E3E19DA7C978E1D016DE2E9078E1F50C1
• Release 1.9.2 is actually signed with: D91A82DB310E8E07519C298A9877C26A3CD36409

curl -sL https://github.com/tpm2-software/tpm2-pkcs11/releases/download/1.9.2/tpm2-pkcs11-1.9.2.tar.gz.asc -o test.asc 
curl -sL https://github.com/tpm2-software/tpm2-pkcs11/releases/download/1.9.2/tpm2-pkcs11-1.9.2.tar.gz -o test.tar.gz 
gpg --verify test.asc test.tar.gz

gpg: Signature made Tue Sep 30 16:28:06 2025 CEST
gpg:                using ECDSA key D91A82DB310E8E07519C298A9877C26A3CD36409
gpg: Good signature from "Bill Roberts (Bills Personal Dev Key) <bill.c.roberts@gmail.com>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: D91A 82DB 310E 8E07 519C  298A 9877 C26A 3CD3 6409

Both keys seem to belong to the same maintainer and can be imported from GitHub:

curl -s "https://github.com/williamcroberts.gpg" | gpg --import

As I am not sure of what the timeline is between both keys, I did not open a PR.
Anyway just letting you know.

Thanks for maintaining the project !