ux: enable Use monospace font only in text editor by default

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/ViewModels/Preferences.cs

@@ -661,7 +661,7 @@ private bool RemoveInvalidRepositoriesRecursive(List<RepositoryNode> collection)
         private string _themeOverrides = string.Empty;
         private string _defaultFontFamily = string.Empty;
         private string _monospaceFontFamily = string.Empty;
-        private bool _onlyUseMonoFontInEditor = false;
+        private bool _onlyUseMonoFontInEditor = true;
         private double _defaultFontSize = 13;
         private double _editorFontSize = 13;
         private int _editorTabWidth = 4;