Update build-and-test.yml changed runner to ubuntu-20.04

Author: alecgn

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

@@ -5,14 +5,14 @@ on:
             - develop
 jobs:
   build-and-test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
 
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: '8.x.x'
+        dotnet-version: '8.0.x'
 
     - name: Build
       run: dotnet build --configuration Release src/MsSqlHelpers/MsSqlHelpers.csproj