Revert "Build with OpenJDK 9 -target 1.8 by default (attempt 3)."

After this revert CL topic, the default toolchain for Android
goes back to being OpenJDK 8.

This revert is being prepared ahead of time in case of
any problems with original change topic.

Bug: 69449021
Test: Treehugger
Change-Id: Ifcefbc1e1357dbe255686e2aeb7a71112d799219