Suppress deprecation warnings for XFA.
Suppress deprecation warnings for XFA.

Temporary measure until FX fixes these (or I do).
This is blocking rolling XFA into chrome.

R=dsinclair@chromium.org

Review URL: https://codereview.chromium.org/1764503003 .

DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium