plug-ins: vectorize and apply-masks checked by default for PDF export.

They used to be TRUE by default but that was overwritten. This has been
fixed in commit c08cf41. Let's bring these defaults back.

plug-ins/common/file-pdf-save.c

@@ -259,9 +259,9 @@ static PdfMultiPage multi_page;
 
 static PdfOptimize optimize =
 {
-  FALSE, /* vectorize */
+  TRUE,  /* vectorize */
   TRUE,  /* ignore_hidden */
-  FALSE, /* apply_masks */
+  TRUE,  /* apply_masks */
   FALSE  /* layers_as_pages */
 };