Platform installation offer is made redundantly when unplugging board

[per1234]

Describe the problem

Arduino IDE has a helpful feature where the boards platform installation is offered automatically under the following conditions:

• An identifiable (via the USB VID/PID pair) board is connected to the user's computer
• The boards platform supporting that board is not already installed

🐛 The installation offer notification appears again when the user disconnects the board from their computer.
They already were shown the notification when the board was connected. Being shown the notification once more on disconnection is unexpected.

To reproduce

Equipment

• Any modern official Arduino board other than the classic Nano

Steps

1. If it is already installed, use "Boards Manager" to uninstall the platform of the board.
2. Connect the Arduino board to your computer.
3. Select the board from the "Board Selector".
   🙂 A helpful notification is shown:

   ⓘ The ___ core has to be installed for the currently selected ___ board. Do you want to install it now?

4. Click the X icon on the notification.
5. Unplug the board from your computer

🐛 The same notification appears again unexpectedly:

ⓘ The ___ core has to be installed for the currently selected ___ board. Do you want to install it now?

Expected behavior

Platform installation offer is only shown when the board is connected to the computer.

Arduino IDE version

2.0.0-beta.11

Operating system

All

Operating system version

N/A

Issue checklist

• I searched for previous reports in the issue tracker
• My report contains all necessary details

[per1234]

Fixed by #485