docs: update win docs re: wsl2; 20.04 -> 24.04

Author: sneurlax

docs/building.md

@@ -275,7 +275,7 @@ flutter run macos
 Visual Studio is required for Windows development with the Flutter SDK.  Download it at https://visualstudio.microsoft.com/downloads/ and install the "Desktop development with C++", "Linux development with C++", and "Visual C++ build tools" workloads.  You may also need the Windows 10, 11, and/or Universal SDK workloads depending on your Windows version.
 
 ### Build plugins in WSL2
-Set up Ubuntu 20.04 in WSL2.  Follow the entire Linux host section in the WSL2 Ubuntu 20.04 host to get set up to build.  The Android Studio section may be skipped in WSL (it's only needed on the Windows host).
+Set up Ubuntu 24.04 in WSL2.  Follow the entire Linux host section in the WSL2 Ubuntu 24.04 host to get set up to build.  The Android Studio section may be skipped in WSL (it's only needed on the Windows host).
 
 Install the following libraries:
 ```