[shotwell] Fix more deprecated functions

[Jens Georg <jensgeorg src gnome org>]

commit 644e5f76d39c6b6bd0c92064a845375b116a403f
Author: Jens Georg <mail jensge org>
Date:   Sat Sep 8 17:17:34 2018 +0200

    Fix more deprecated functions

 src/Printing.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/Printing.vala b/src/Printing.vala
index 988a4567..da46b08d 100644
--- a/src/Printing.vala
+++ b/src/Printing.vala
@@ -683,7 +683,7 @@ public class CustomPrintTab : Gtk.Box {
     }
 
     private void set_print_titles_font(string fontname) {
-        title_print_font.set_font_name(fontname);
+        (title_print_font as Gtk.FontChooser).set_font(fontname);
     }
 
 
@@ -696,7 +696,7 @@ public class CustomPrintTab : Gtk.Box {
     }
 
     private string get_print_titles_font() {
-        return title_print_font.get_font_name();
+        return (title_print_font as Gtk.FontChooser).get_font();
     }
 
     public PrintJob get_source_job() {