Docs: dampen story time for atomics

Story time was nice a few years ago, but by now it's nice to state how things are, rather than explain the diff from ye olden atomic history. These were dark times.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265369 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed