Remove --experimental_enable_repo_mapping. (#311)
Remove --experimental_enable_repo_mapping. (#311)

bazel 0.24.1 doesn't support it, and we haven't used it since
commit 11f65c83459b4d2aafe47feed16bf458a5c3b088.
census-instrumentation/opencensus-cpp,census-instrumentation/opencensus-cpp,census-instrumentation/opencensus-cpp,census-instrumentation/opencensus-cpp