Fix UI overlapping and void space in the full widgets picker

The issue is caused by not updating the header container after widgets
recycler view items changed due to item click.

Test: Expand / collapse items in the full widgets picker. No UI
      overlapping or void space is observed.
Bug: 186121915
Change-Id: I6a12bbdcca921d66c6d62601bb59cea66a33640b
2 files changed