fix: correctly handle updating/removing non-zero start lines

Unfortuantely the default treesitter start() gives us the slightly wrong
lines for purposes of virtual indent. We need to grab one line less if
the start line gathered is non zero

lua/orgmode/ui/virtual_indent.lua

@@ -61,7 +61,10 @@ function VirtualIndent:set_indent(bufnr, start_line, end_line, ignore_ts)
       end
     end
   end
-  self:_delete_old_extmarks(bufnr, start_line - 1, end_line)
+  if start_line > 0 then
+    start_line = start_line - 1
+  end
+  self:_delete_old_extmarks(bufnr, start_line, end_line)
   for line = start_line, end_line do
     local indent = self:_get_indent_size(line)