Change mailing list names in README

An underscore is used in the mailing list names rather than a dash, so it is
parallel_libs instead of parallel-libs.

llvm-svn: 273742
GitOrigin-RevId: babc13a3e25636bd6b9ee64baf42bca1a8e497cf
1 file changed
tree: 46451446712c7e96b3ca9fe37cc23f804bdee321
  1. README.rst