Update Trusted Signing URL to Microsoft Learn

Replaced the URL in the `linkLabelReadMoreTrustedSigning_LinkClicked` method to point to `Globals.ToolStings.URLMicrosoftLearnTrustedSigning` instead of `Globals.ToolStings.URLAzurePortalTrustedSigning`. Updated both the `Process.Start` call and the error message in `MessageBox.Show` to reflect the new URL.

Author: michaelmsonne

src/SignToolGUI/Forms/MainForm.cs

@@ -2156,15 +2156,15 @@ private void linkLabelReadMoreTrustedSigning_LinkClicked(object sender, LinkLabe
         {
             try
             {
-                Process.Start(Globals.ToolStings.URLAzurePortalTrustedSigning);
+                Process.Start(Globals.ToolStings.URLMicrosoftLearnTrustedSigning);
 
                 // Log the opening of the URL message
                 Message("User clicked the 'Read more' link for Trusted Signing to open the URL: '" + Globals.ToolStings.URLMicrosoftLearnTrustedSigning + "'", EventType.Information, 1052);
             }
             catch (Exception ex)
             {
                 // Show an error message if the URL could not be opened
-                MessageBox.Show(@"Failed to open the URL '" + Globals.ToolStings.URLAzurePortalTrustedSigning + "'. Error: " + ex.Message, @"Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
+                MessageBox.Show(@"Failed to open the URL '" + Globals.ToolStings.URLMicrosoftLearnTrustedSigning + "'. Error: " + ex.Message, @"Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
 
                 // Log the error message
                 Message("Failed to open the URL: " + ex.Message, EventType.Error, 1041);