fix: remove Content-Length header for non-2xx image responses

it's a lie

src/invidious/routes/images.cr

@@ -155,7 +155,9 @@ module Invidious::Routes::Images
     env.response.headers["Access-Control-Allow-Origin"] = "*"
 
     if response.status_code >= 300
-      return env.response.headers.delete("Transfer-Encoding")
+      env.response.headers.delete("Content-Length")
+      env.response.headers.delete("Transfer-Encoding")
+      return
     end
 
     return Helpers.proxy_file(response, env)