Rip out context_hosts checks

The remote host is now encoded in the builder name so we don't need
to check it. We'll just do an inspect to confirm the builder exists.

lib/kamal/commands/builder.rb

@@ -1,8 +1,7 @@
 require "active_support/core_ext/string/filters"
 
 class Kamal::Commands::Builder < Kamal::Commands::Base
-  delegate :create, :remove, :push, :clean, :pull, :info, :context_hosts, :config_context_hosts, :validate_image,
-           :first_mirror, to: :target
+  delegate :create, :remove, :push, :clean, :pull, :info, :buildx_inspect, :validate_image, :first_mirror, to: :target
 
   include Clone