Dump native builder

We already ensure that buildx is installed, so let's always use it.

lib/kamal/commands/builder.rb

@@ -13,7 +13,7 @@ class Kamal::Commands::Builder < Kamal::Commands::Base
   def target
     case
     when !config.builder.multiarch? && !config.builder.cached?
-      native
+      local
     when !config.builder.multiarch? && config.builder.cached?
       local
     when config.builder.local? && config.builder.remote?
@@ -25,10 +25,6 @@ class Kamal::Commands::Builder < Kamal::Commands::Base
     end
   end
 
-  def native
-    @native ||= Kamal::Commands::Builder::Native.new(config)
-  end
-
   def remote
     @remote ||= Kamal::Commands::Builder::Remote.new(config)
   end

lib/kamal/commands/builder/native.rb

@@ -1,20 +0,0 @@
-class Kamal::Commands::Builder::Native < Kamal::Commands::Builder::Base
-  def create
-    # No-op on native without cache
-  end
-
-  def remove
-    # No-op on native without cache
-  end
-
-  def info
-    # No-op on native
-  end
-
-  def push
-    combine \
-      docker(:build, *build_options, build_context),
-      docker(:push, config.absolute_image),
-      docker(:push, config.latest_image)
-  end
-end