Update test.yml

fix dotnet-format version to 6.0.243104 which is the last that supports netcoreapp3.1, the next v6.x supports only net6

Author: sungam3r

.github/workflows/test.yml

@@ -59,7 +59,7 @@ jobs:
         if: ${{ startsWith(matrix.os, 'ubuntu') }}
         working-directory: src
         run: |
-          dotnet tool install -g dotnet-format --version 6.0.* --add-source https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json
+          dotnet tool install -g dotnet-format --version 6.0.243104 --add-source https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json
           dotnet format --check --fix-whitespace || (echo "Run 'dotnet format' to fix formatting issues" && exit 1)
           dotnet format --check -v diag --fix-style warn --fix-analyzers warn || (echo "Run 'dotnet format' to fix formatting issues" && exit 1)
       - name: Build solution [Release]