fix(render): disable underline for diagnostics (#1478)

Problem: On current Nvim nightlies, a regression in a
`vim.highlight.range()` refactor makes underlines for diagnostics at end
of line extend into the next line, leading to visual artifacts in the
update view.

Solution: Suppress underlines for diagnostics, as they are not wanted
anyway.

lua/lazy/view/render.lua

@@ -84,7 +84,7 @@ function M:update()
       diag.lnum = diag.row - 1
       return diag
     end, self._diagnostics),
-    { signs = false, virtual_text = true }
+    { signs = false, virtual_text = true, underline = false }
   )
 end