simplify URL validation

app/src/main/res/values/strings.xml

@@ -43,5 +43,4 @@
   <string name="hidden_app_name">Device Settings</string>
   <string name="hidden_alert">The app has been hidden. To open it again please dial 8722227 (TRACCAR).</string>
   <string name="error_msg_invalid_url">Please enter a valid http:// or https:// URL</string>
-  <string name="error_invalid_url_summary">Invalid server URL</string>
 </resources>