Revert "Add Apple Touch icon for Labs"

We keep Labs's favicon.ico in the labs/toollabs repository, and that
is where Apple Touch icons for Labs should probably reside as well.

This reverts commit d007275f00a757cad9dd4dcc6f17bc7da68eb9de.

Bug: 52583
Change-Id: If18d4215b603f5461451c27ccb8e2a8165f2b0d0