Use specific SDK version

Use `7.0.100` explicitly.

Author: martincostello

.github/workflows/build.yml

@@ -36,7 +36,7 @@ jobs:
     - name: Setup .NET SDK
       uses: actions/setup-dotnet@v3
       with:
-        dotnet-version: '7.0.x'
+        dotnet-version: '7.0.100'
 
     - name: Test
       run: |