SourceView: remove unused variables (#1580)

Co-authored-by: Jeremy Wootten <jeremywootten@gmail.com>

Author: danirabbit

src/Widgets/SourceView.vala

@@ -38,8 +38,6 @@ namespace Scratch.Widgets {
         private string selected_text = "";
         private GitGutterRenderer git_diff_gutter_renderer;
         private NavMarkGutterRenderer navmark_gutter_renderer;
-        private Gtk.TextMark? current_edit_point = null;
-        private int last_edit_point_line = 0;
 
         private const uint THROTTLE_MS = 400;
         private double total_delta = 0;