Remove RBS/Steep, add under-development warning to README

Author: cretz

Gemfile

@@ -7,7 +7,5 @@ gem 'temporalio', path: '../temporal-sdk-ruby'
 group :development do
   gem 'minitest'
   gem 'rake'
-  gem 'rbs', '~> 3.5.3'
   gem 'rubocop'
-  gem 'steep', '~> 1.7.1'
 end

README.md

@@ -2,6 +2,11 @@
 
 This is the set of Ruby samples for the [Ruby SDK](https://github.com/temporalio/sdk-ruby).
 
+⚠️ UNDER ACTIVE DEVELOPMENT
+
+The Ruby SDK is under active development and has not released a stable version yet. APIs may change in incompatible ways
+until the SDK is marked stable.
+
 ## Usage
 
 Prerequisites:

Rakefile

@@ -13,15 +13,4 @@ require 'rubocop/rake_task'
 
 RuboCop::RakeTask.new
 
-require 'steep/rake_task'
-
-Steep::RakeTask.new
-
-namespace :rbs do
-  desc 'RBS tasks'
-  task :install_collection do
-    sh 'rbs collection install'
-  end
-end
-
 task default: %w[rubocop test]