Don't perform config change if relayoutAsync

mPendingMergedConfiguration wouldn't be updated if we didn't call
IWindowSession#relayout.

Bug: 244003094
Test: atest ToggleDarkThemeMicrobenchmark#testToggle
Change-Id: Ibc2f40dd986136d9b54f3a7f491f7517489e05af
1 file changed