Bug 1893270 followup: save a copy of the cairo patch in-tree. a=dmeehan

diff --git a/gfx/cairo/cairo/src/cairo-cff-subset.c b/gfx/cairo/cairo/src/cairo-cff-subset.c

--- a/gfx/cairo/cairo/src/cairo-cff-subset.c

+++ b/gfx/cairo/cairo/src/cairo-cff-subset.c

@@ -3154,7 +3154,7 @@ static cairo_int_status_t

     cairo_status_t status;

     cairo_cff_font_t *font;

-    font = _cairo_malloc (sizeof (cairo_cff_font_t));

+    font = calloc (1, sizeof (cairo_cff_font_t));

     if (unlikely (font == NULL))

 	return _cairo_error (CAIRO_STATUS_NO_MEMORY);