Fix tests to expect new error message.

Respond to dotnet/runtime#88974

Author: eerhardt

src/Servers/Kestrel/test/Interop.FunctionalTests/HttpClientHttp2InteropTests.cs

@@ -629,7 +629,7 @@ public async Task ServerReset_AfterHeaders_ClientBodyThrows(string scheme)
         response.EnsureSuccessStatusCode();
         receivedHeaders.SetResult();
         var exception = await Assert.ThrowsAsync<HttpRequestException>(() => response.Content.ReadAsStringAsync()).DefaultTimeout();
-        Assert.Equal("The HTTP/2 server reset the stream. HTTP/2 error code 'CANCEL' (0x8).", exception?.InnerException?.Message);
+        Assert.Equal("The HTTP/2 server reset the stream. HTTP/2 error code 'CANCEL' (0x8). (HttpProtocolError)", exception?.InnerException?.Message);
         await host.StopAsync().DefaultTimeout();
     }