Revert "Make dokka compile with Kotlin 1.5" am: 2d1d7e3f35 am: 1659fc3898 am: cf04b58f72 am: 5c9765afee

Original change: https://android-review.googlesource.com/c/platform/external/dokka/+/1705628

Change-Id: I7f518df08bdf7793775233d64d3dd793b9579ab3