HaikuDepot: Text: Fix regression for B_SELECT_ALL

An Invalidate() was removed, since I originally planned to remove the need
to invalidate on selection changes, but then saved it for later.

src/apps/haikudepot/textview/TextDocumentView.cpp

@@ -369,6 +369,7 @@ TextDocumentView::SelectAll()
 
 	fTextEditor->SelectAll();
 	_ShowCaret(false);
+	Invalidate();
 }