chore: remove dotnet 5.x from release matrix

Author: bojidar-bg

.github/workflows/release-agent-dotnet.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        dotnet: ['5.0.x', '6.0.x']
+        dotnet: ['6.0.x']
 
     steps:
       - uses: actions/checkout@v1