[ci]Sign OpenAI dll that's not signed (#36299)

.pipelines/ESRPSigning_core.json

@@ -327,6 +327,7 @@
                 "WinUI3Apps\\TestableIO.System.IO.Abstractions.dll",
                 "TestableIO.System.IO.Abstractions.Wrappers.dll",
                 "WinUI3Apps\\TestableIO.System.IO.Abstractions.Wrappers.dll",
+                "WinUI3Apps\\OpenAI.dll",
                 "ColorCode.Core.dll", 
                 "ColorCode.UWP.dll",
                 "UnitsNet.dll",