"Reset Priorities" functionality is not working for "Quick Search" under the "Provider Settings" in the "Preferences" window.

Steps to repro:
1. Create a new project
2. Window > Package Manager > Quick Search > Install(preview.4 - 1.6.0)
3. Edit > Preferences > Quick Search
4. Change the priorities of property under "Provider Settings"
5. Click on "Reset Priorities" button

Actual Result:
"Reset Priorities" functionality is broken

Expected Result:
Priorities of property should reset on selecting "Reset Priorities" button

Occurring on:
2020.2.0a4, 2020.1.0b3 with package version preview.4 - 1.6.0

Working fine on:
2020.2.0a4, 2020.1.0b3 with package version preview.3 - 1.6.0, 1.5.2

Environment:
Windows 10 and macOS 10.14