Revert "[SCEV] Clarify behavior around max backedge taken count"

This reverts commit r303497 since it breaks the msan bootstrap bot:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/1379/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303498 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed