Pasted value is duplicated in Sync: Advanced Options > Sync: Open Settings

[tom0dea]

🐛 Describe the bug
When you paste a text value into the settings screen, the value is duplicated.

🌴 Visual Studio Code Version : 1.47.0
🌴 Code Settings Sync Version : 3.4.3
🌴 Standard or Insiders : Standard
🌴 Portable or Installed : Installed
🌴 OSS or Official Build : Official
🌴 Operating System : Windows 7
🌴 Occurs On: Help Configuring
🌴 Proxy Enabled: NO
🌴 Gist Id: N/A

📰 To Reproduce

1. Go to Sync: Advanced Options > Sync: Open Settings
2. Copy your token, gist id or an text value (Ctrl+C)
3. Paste the token or gist id into the appropriate field (Ctrl+V)
4. The copied value is duplicated in the field. 1234 becomes 12341234

💪 Expected behavior
Pasted value is not duplicated.

Screenshot of settings screen: