Disable FOLDABLE_SINGLE_PAGE

ENABLE_TWO_PANEL_HOME is no longer used so I will also
remove it.

TwoPanelWorkspaceTest was expecting an icon on the hotseat
which no longer exist.

We will use the new flag system in main for this
feature.

Test: atest ReorderWidgets
Test: atest FoldableIntegrity
Bug: 270395274
Change-Id: I122a924a81ae989ff5636d8e276d6d31bbe0877d