[release/4.0] Update release-4.0.3.md (#7536)

* Update release-4.0.3.md

* Update docs/release-notes/4.0.3/release-4.0.3.md

Co-authored-by: Copilot <[email protected]>

---------

Co-authored-by: Eric StJohn <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

docs/release-notes/4.0.3/release-4.0.3.md

@@ -1,8 +1,21 @@
 # [ML.NET](http://dot.net/ml) 4.0.3
 
-## **Enhancements**
+## **Bug Fixes**
 - **[release/4.0] Improve unique directory generation for temp files** ([#7528](https://github.com/dotnet/machinelearning/pull/7528))
+  - Compatibility note: This change resolves a performance problem where past versions of ML.NET would leave behind folders with the pattern `ml_dotnet\d+` in the temp directory, which would cause model opening performance to degrade.  This fixes the problem.  You may also wish to delete these empty folders once after updating.
+
+    Using powershell:
+    ```powershell
+    Get-ChildItem "$env:TEMP" -Directory -Filter "ml_dotnet*" | Remove-Item -Recurse -Force
+    ```
+
+    Using Bash:
+    ```bash
+    find "$TEMP" -type d -name "ml_dotnet*" -exec rm -rf {} +
+    ```
+    
 
 
 ## **Build / Test updates**
 - **[release/4.0] Update dependencies from dotnet/arcade** ([#7470](https://github.com/dotnet/machinelearning/pull/7470))
+- **[release/4.0] Use arcade script for installing MacOS dependencies** ([#7534](https://github.com/dotnet/machinelearning/pull/7534))