[ApplicationInsights] Fix namespace and output folder for .NET (#19119)

Correct the namespace and output folder for .NET.
NOTE: This could be a breaking change.

Author: HarveyLink

specification/applicationinsights/resource-manager/readme.md

@@ -632,8 +632,8 @@ csharp:
   azure-arm: true
   payload-flattening-threshold: 1
   license-header: MICROSOFT_MIT_NO_VERSION
-  namespace: Microsoft.Azure.Management.ApplicationInsights.Management
-  output-folder: $(csharp-sdks-folder)/applicationinsights/Microsoft.Azure.ApplicationInsights/src/Generated
+  namespace: Microsoft.Azure.Management.ApplicationInsights
+  output-folder: $(csharp-sdks-folder)/applicationinsights/Microsoft.Azure.Management.ApplicationInsights/src/Generated
   clear-output-folder: true
 ```