[NFC] Add upcoming release section post 1.9 release (#8107)

Add an 'Upcoming Release' section back into the release notes.

---------

Co-authored-by: Steven Perron <stevenperron@google.com>
Co-authored-by: Nathan Gauër <brioche@google.com>

Author: 3 people

docs/ReleaseNotes.md

@@ -17,14 +17,10 @@ The included licenses apply to the following files:
 
 ## Changelog
 
-### Version 1.9.2602
-
-#### Shader Model 6.9 Release
+### Upcoming Release
 
-- Shader Model 6.9 is fully supported.
-  - See [the official blog
-  post](https://devblogs.microsoft.com/directx/shader-model-6-9-dxr-1-2-and-agilitysdk-1-619-release)
-  for more details.
+Place release notes for the upcoming release below this line and remove this
+line upon naming the release. Refer to previous for appropriate section names.
 
 #### Experimental Shader Model 6.10
 
@@ -36,6 +32,15 @@ The included licenses apply to the following files:
   shaders which returns the total number of waves executing within the thread
   group.
 
+### Version 1.9.2602
+
+#### Shader Model 6.9 Release
+
+- Shader Model 6.9 is fully supported.
+  - See [the official blog
+  post](https://devblogs.microsoft.com/directx/shader-model-6-9-dxr-1-2-and-agilitysdk-1-619-release)
+  for more details.
+
 #### Noteble SPIR-V updates
 
 - Handle vector element assignment for asuint. [#8011](https://github.com/microsoft/DirectXShaderCompiler/issues/8011)