Remove maven-metadata files from prebuilts.

Test: cd tools && ./gradlew :init check && cd idea && ant test && \
cd ../.. && cat tools/base/bazel/test_targets | xargs bazel test \
'--genrule_strategy=standalone' '--spawn_strategy=standalone'

Change-Id: I8ffa30ef278932a420a956193a0e6ab191646636
294 files changed