Use https URLs to access renderdoc.org

* Previous versions accessing the http URLs will be redirected soon (as
  of time of writing this). The POST /bugsubmit won't be redirected as
  it's not feasible to redirect POST requests, but that will continue
  working.

renderdocui/Windows/MainWindow.cs

@@ -1112,7 +1112,7 @@ namespace renderdocui.Windows
             var updateThread = Helpers.NewThread(new ThreadStart(() =>
             {
                 // spawn thread to check update
-                WebRequest g = HttpWebRequest.Create(String.Format("http://renderdoc.org/getupdateurl/{0}/{1}", IntPtr.Size == 4 ? "32" : "64", versionCheck));
+                WebRequest g = HttpWebRequest.Create(String.Format("https://renderdoc.org/getupdateurl/{0}/{1}", IntPtr.Size == 4 ? "32" : "64", versionCheck));
 
                 UpdateResult result = UpdateResult.Disabled;