`ActiveRecord::Associations::CollectionProxy#build` has incorrect block signature

[clinejj]

When creating a new ActiveRecord model through an association, for example:

class Post < ActiveRecord::Base
  has_many comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

post = Post.new
comment = post.comments.new

the current type definitions throw an error when validating in Steep due to an incorrect signature:

 [error] The method cannot be called without a block
│ Diagnostic ID: Ruby::RequiredBlockMissing
│
└     @comment = post.comments.new
                               ~~~

This specific one comes from ActiveRecord::Associations::CollectionProxy#new(build), which is defined on https://github.com/ruby/gem_rbs_collection/blob/main/gems/activerecord/6.0/activerecord-generated.rbs#L1156-L1158

      def build: (?::Hash[untyped, untyped] attributes) { () -> untyped } -> untyped

      alias new build

The patch to fix it is to make the block optional, ie ?{ () -> untyped }

There is another method definition under ActiveRecord::AssociationRelation that likely also needs to be updated: https://github.com/ruby/gem_rbs_collection/blob/main/gems/activerecord/6.0/activerecord-generated.rbs#L259-L261

I'm happy to make a PR to address, but not sure if you would prefer to update the generated files or the patch.