Disable lazy images for now

The feature is very unstable on Zola's side, it causes a lot of
rendering issues that I don't know how to fix because it's not an issue
on my end.

config.toml

@@ -32,7 +32,6 @@ highlight_themes_css = [
   { theme = "solarized-light", filename = "syntax-theme-light.css" },
 ]
 smart_punctuation = true
-lazy_async_image = true
 bottom_footnotes = true
 
 [search]