Updated kernel release notes

Author: craigloewen-msft

WSL/kernel-release-notes.md

@@ -11,6 +11,13 @@ ms.localizationpriority: high
 
 We've added support for WSL 2 distributions, [which use a full Linux kernel](https://devblogs.microsoft.com/commandline/shipping-a-linux-kernel-with-windows/). This Linux kernel is open source, with its source code available at the [WSL2-Linux-Kernel](https://github.com/microsoft/WSL2-Linux-Kernel) repository. This Linux kernel is delivered to your machine via Microsoft Update, and follows a separate release schedule to the Windows Subsystem for Linux which is delivered as part of the Windows image.
 
+## 5.4.51-microsoft-standard
+*Release Date*: Prerelease - 10/22/2020
+
+[Official Github release link](https://github.com/microsoft/WSL2-Linux-Kernel/releases/tag/linux-msft-5.4.51).
+
+* Stable release of 5.4.51
+
 ## 4.19.128-microsoft-standard
 *Release Date*: 09/15/2020