chore: Add back .NET 5 SDK

.vsts-ci.yml

@@ -11,6 +11,13 @@ jobs:
   - checkout: self
     clean: true
 
+  - task: UseDotNet@2
+    displayName: 'Use .NET Core SDK 5.0.x'
+    retryCountOnTaskFailure: 3
+    inputs:
+      packageType: sdk
+      version: 5.0.x
+
   - task: UseDotNet@2
     displayName: 'Use .NET SDK 7.0.203'
     retryCountOnTaskFailure: 3