Fix licenses in headers to pass Chromium's checklicenses tool.

This is a re-landing of the changes in https://pdfium.googlesource.com/pdfium/+/6387aff
which were lost during a libopenjpeg library roll.

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/661463003
2 files changed