Try bumping to latest SDK

Author: JimBobSquarePants

.github/workflows/build-and-test.yml

@@ -111,7 +111,7 @@ jobs:
         uses: actions/setup-dotnet@v4
         with:
           dotnet-version: |
-            8.0.x
+            9.0.x
             7.0.x
             6.0.x
 

.github/workflows/code-coverage.yml

@@ -61,7 +61,7 @@ jobs:
         uses: actions/setup-dotnet@v4
         with:
           dotnet-version: |
-            8.0.x
+            9.0.x
             7.0.x
             6.0.x