Fix typo in WiFi dialog (#1853)

Resolves #1852

This change removes the second colon in the Wi-Fi dialog when it warns
there's no Ethernet connection.

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app/templates/custom-elements/wifi-dialog.html

@@ -73,7 +73,7 @@ <h3>Wi-Fi Credentials</h3>
       credentials.
     </p>
     <inline-message variant="warning" id="no-ethernet-warning">
-      <strong>Warning:</strong>: You are currently connected to your TinyPilot
+      <strong>Warning:</strong> You are currently connected to your TinyPilot
       device using Wi-Fi. If you change your settings, you might get
       disconnected. Consider connecting an Ethernet cable before proceeding.
     </inline-message>