Revert "Temporarily remove dotnet run argument separator"

This reverts commit 5f9fa5c.

Author: kichalla

src/Microsoft.AspNetCore.Server.IntegrationTesting/Deployers/ApplicationDeployer.cs

@@ -22,9 +22,7 @@ public abstract class ApplicationDeployer : IApplicationDeployer
 
         // This is the argument that separates the dotnet arguments for the args being passed to the
         // app being run when running dotnet run
-        // Temporarily remove separator to workaround "dotnet run no longer passes additional arguments
-        // to application" (https://github.com/dotnet/sdk/issues/1118)
-        public static readonly string DotnetArgumentSeparator = "";
+        public static readonly string DotnetArgumentSeparator = "--";
 
         private readonly Stopwatch _stopwatch = new Stopwatch();