[Package manager] Package manager window does not become fullscreen when maximized

The undocked Package manager window does not become fullscreen (in height )when maximized with the green maximize button on the top left side of the package manager window and due to which buttons on the bottom of the package manager window are inactive.

Steps to Reproduce:
1. Create a new Project
2. Open Window > Package Manager
3. Undock Package Manager window
4. Manager window > maximize ( green maximize button on the top left side of package manager window )
5. Observe the Package manager window does not become fullscreen (in height)

Expected Result: window becomes fullscreen

Actual Result: window does not become fullscreen (in height )

Reproducible on: 2020.2.0b3, 2020.2.0b2

Working fine on: 2020.2.0b1, 2020.1, 2019.4, 2018.4

Environment: Mac 10.15