enhance: disable AllowScrollBelowDocument option for text diff view (sourcegit-scm#1801)

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

Author: love-linger

src/Views/TextDiffView.axaml.cs

@@ -521,6 +521,7 @@ public ThemedTextDiffPresenter(TextArea area, TextDocument doc) : base(area, doc
             Options.EnableHyperlinks = false;
             Options.EnableEmailHyperlinks = false;
             Options.ShowEndOfLine = false;
+            Options.AllowScrollBelowDocument = false;
 
             _lineStyleTransformer = new LineStyleTransformer(this);