[SB] Fix StatusBarContentInsetsViewModelTest

The contentArea_onMaxBoundsChanged_emitsNewValue test can fail
if the configuration is already RTL=true.
This fix ensures we explictly set RTL=false in the test setup.

Test: StatusBarContentInsetsViewModelTest
Bug: 437437516
Flag: com.android.systemui.status_bar_root_modernization
Change-Id: Ifc2c1fcd05f0a9a9070f0f495c4731750f19cf64