[GlobalMerge] Fix a typo

now => know

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330965 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/GlobalMerge.cpp

@@ -242,7 +242,7 @@ bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
   // code (currently, a Function) to the set of globals seen so far that are
   // used together in that unit (GlobalUsesByFunction).
   //
-  // When we look at the Nth global, we now that any new set is either:
+  // When we look at the Nth global, we know that any new set is either:
   // - the singleton set {N}, containing this global only, or
   // - the union of {N} and a previously-discovered set, containing some
   //   combination of the previous N-1 globals.