[MinGW] Set the right updated option help for the updated pdb option. NFC
[MinGW] Set the right updated option help for the updated pdb option. NFC

I forgot to amend this change before committing it in SVN r361014, this
is what was agreed upon in the review.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@361093 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld