Fix comment typo.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@188045 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Fully cover the switch for COMDAT attributes and add a comment.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@188046 91177308-0d34-0410-b5e6-96231b3b80d8