[2/n] Update default initial bounds scale to 72% (from 75%)

Currently, default initial bounds are based off 75% device screen size. We are changing it to 72% of device screen size to align with the updated UI/UX specifications.

Flag: EXEMPT approved by product & UX teams
Test: atest WmTests:DesktopModeLaunchParamsModifierTests, atest WMShellUnitTests:DesktopTasksControllerTest
Bug: 399581767
Change-Id: Ia3451b47d3b5247a10f2e4f90396521df0d9aa79