Revert "Pin various layoutlib targets to Java language level 8 on layoutlib branches."

Layoutlib was pinned to Java language level 8 because Android Studio was
running using OpenJDK 8. That is not necessary any more as Android Studio
is moving to OpenJDK 11. So layoutlib can use the default Android toolchain
settings.

This reverts commit b3b31f585ef39f5f19d29778fd5e862a8842ec85.

Bug: 142116384
Test: run layoutlib tests
Change-Id: I790c9dfe251c80f80d4bcc3e19d6fff84f2086f1
3 files changed