[Gardening] Updated comment.

Author: nate-chandler

lib/SILOptimizer/SemanticARC/BorrowScopeOpts.cpp

@@ -47,8 +47,8 @@ bool SemanticARCOptVisitor::visitBeginBorrowInst(BeginBorrowInst *bbi) {
   if (!ctx.shouldPerform(ARCTransformKind::RedundantBorrowScopeElimPeephole))
     return false;
 
-  // Lexical borrow scopes must remain in order to ensure that value lifetimes
-  // are not observably shortened.
+  // Non-redundant, lexical borrow scopes must remain in order to ensure that
+  // value lifetimes are not observably shortened.
   if (bbi->isLexical() && !isRedundantLexicalBeginBorrow(bbi)) {
     return false;
   }