Update menu item text based on signing mode

Updated the `manageTimestampServersToolStripMenuItem` text to reflect the selected signing mode:
- "Manage Endpoints..." for Trusted Signing mode.
- "Manage Timestamp Servers..." for regular signing mode.

This change improves user clarity by dynamically adjusting the menu item text to match the current signing context.

Author: michaelmsonne

src/SignToolGUI/Forms/MainForm.cs

@@ -2344,6 +2344,9 @@ private void RadioButtonSelectCertificateLocation_CheckedChanged(object sender,
 
                 // Set the tooltip for the timestamp checkbox
                 toolTip.SetToolTip(checkBoxTimestamp, "Trusted Signing requires a timestamp. This option is disabled for Trusted Signing.");
+
+                // Update menu item text for Trusted Signing mode
+                manageTimestampServersToolStripMenuItem.Text = "Manage Endpoints...";
             }
             else
             {
@@ -2369,6 +2372,9 @@ private void RadioButtonSelectCertificateLocation_CheckedChanged(object sender,
 
                 // Reset the tooltip for the timestamp checkbox
                 toolTip.SetToolTip(checkBoxTimestamp, "Check this box to timestamp the signed file(s).");
+
+                // Update menu item text for regular timestamp servers mode
+                manageTimestampServersToolStripMenuItem.Text = "Manage Timestamp Servers...";
             }
 
             // Check if the rest checkboxes are enabled and set handling correctly for signing type