[gedit-latex] Do not rely on deprecated Gedit.Document.get_encoding()

[Pietro Battiston <pbattiston src gnome org>]

commit 959755c21d9909dafdd639455a1e621063b9c633
Author: Pietro Battiston <pbattiston src gnome org>
Date:   Thu Apr 16 15:33:34 2020 +0200

    Do not rely on deprecated Gedit.Document.get_encoding()

 latex/editor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/latex/editor.py b/latex/editor.py
index 4f7cbe0..953be77 100644
--- a/latex/editor.py
+++ b/latex/editor.py
@@ -286,7 +286,7 @@ class Editor(object):
         """
         Return the character set used by this Editor
         """
-        return self._text_buffer.get_encoding().get_charset()
+        return self._text_buffer.get_file().get_encoding().get_charset()
 
     @property
     def content(self):