Remove .NET {6, 7, 8}.x from CI workflows (build-and-test and publish)

Author: 64J0

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

@@ -32,9 +32,6 @@ jobs:
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: |
-            6.x
-            7.x
-            8.x
             9.x
             10.x
       - name: Restore

.github/workflows/publish.yml

@@ -34,9 +34,6 @@ jobs:
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: |
-            6.x
-            7.x
-            8.x
             9.x
             10.x
       - name: Restore
@@ -56,9 +53,6 @@ jobs:
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: |
-            6.x
-            7.x
-            8.x
             9.x
             10.x
       - name: Create Release NuGet package