removed not supported ner versions

Author: Petr Sramek

.github/workflows/dotnet.yml

@@ -15,7 +15,7 @@ jobs:
 
     strategy:
       matrix:
-        netversion: [5, 6, 7, 8, 9]
+        netversion: [7, 8, 9]
 
     steps:
     - uses: actions/checkout@v3
@@ -60,7 +60,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        netversion: [5, 6, 7, 8, 9]
+        netversion: [7, 8, 9]
 
     runs-on: ${{ matrix.os }}