bump .net 9

Author: w8tcha

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        dotnet-version: [ '8.0.x' ]
+        dotnet-version: [ '9.0.x' ]
 
     steps:
       - uses: actions/checkout@v4