Fix typos in GN error message

Review-Url: https://codereview.chromium.org/2132443002
Cr-Original-Commit-Position: refs/heads/master@{#404084}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8273381e8ba3a0e448715ebfc1232c0ad6ef2fe5
1 file changed
tree: a2f1474278248c856c34893900f268f36cb4b75a
  1. tools/