Remove unused file WidgetsListSearchHeaderHolder

WidgetsListSearchHeaderHolder was the only file that remained after all the redundant widget search header logic got removed. It is dead code now so this CL deletes it.

Bug: 268646258
Test: Verified on device
Change-Id: I670364bd7c2d5ce46d2c8837ef483e5ac2315547
1 file changed