Stop relying on external/dokka/maven prebuilts.
Stop relying on external/dokka/maven prebuilts.

Moving dokka prebuilts to standard prebuilds/androidx/external

Test: ./gradlew distPublicDokkaDocs
Change-Id: Ib1259fb1b55f3ca92315790bf0628960cc2a7ef4

androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx