[llvm-exegesis] Remove noexcept in r335105.

gcc checks for transitivity (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53903)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335109 91177308-0d34-0410-b5e6-96231b3b80d8