Fix never matching clause

`length/1` is only used with lists.

lib/pleroma/clippy.ex

@@ -4,6 +4,7 @@
 
 defmodule Pleroma.Clippy do
   @moduledoc false
+
   # No software is complete until they have a Clippy implementation.
   # A ballmer peak _may_ be required to change this module.
 

lib/pleroma/html.ex

@@ -163,6 +163,7 @@ defmodule Pleroma.HTML.Scrubber.Default do
 
   require FastSanitize.Sanitizer.Meta
   alias FastSanitize.Sanitizer.Meta
+
   # credo:disable-for-previous-line
   # No idea how to fix this one…
 

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -387,7 +387,7 @@ def handle_incoming(%{"type" => "Flag", "object" => objects, "actor" => actor} =
   def handle_incoming(%{"id" => nil}, _options), do: :error
   def handle_incoming(%{"id" => ""}, _options), do: :error
   # length of https:// = 8, should validate better, but good enough for now.
-  def handle_incoming(%{"id" => id}, _options) when not (is_binary(id) and length(id) > 8),
+  def handle_incoming(%{"id" => id}, _options) when is_binary(id) and byte_size(id) < 8,
     do: :error
 
   # TODO: validate those with a Ecto scheme