Remove unnecessary GridDisplayOption_defaultSplitDisplayLayoutId attribute

- Can use deviceCategory to make grid specific to splitDisplay instead
- Update TwoPanelWorkspaceTest for new workspace items

Fix: 233736588
Test: Clear launcher and check the default
Test: TwoPanelWorkspaceTest
Change-Id: I6ad3a2d866d847af281e10b802edbd4bcc892c39