Remove FPDFFormObj_GetMatrix() impl.

It should have been deleted in
https://pdfium-review.googlesource.com/82612.

Change-Id: I1f1c8691cbc47ed0eed260a70bcb4117862cec3e
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/82794
Auto-Submit: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/fpdf_editpage.cpp b/fpdfsdk/fpdf_editpage.cpp
index a74ac9f..696fa21 100644
--- a/fpdfsdk/fpdf_editpage.cpp
+++ b/fpdfsdk/fpdf_editpage.cpp
@@ -978,13 +978,3 @@
   return FPDFPageObjectFromCPDFPageObject(
       pObjectList->GetPageObjectByIndex(index));
 }
-
-FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
-FPDFFormObj_GetMatrix(FPDF_PAGEOBJECT form_object, FS_MATRIX* matrix) {
-  CPDF_FormObject* pFormObj = CPDFFormObjectFromFPDFPageObject(form_object);
-  if (!pFormObj || !matrix)
-    return false;
-
-  *matrix = FSMatrixFromCFXMatrix(pFormObj->form_matrix());
-  return true;
-}