add opentelemetry-test-helpers and rake as development dependencies

Author: michal-kazmierczak

instrumentation/grpc/opentelemetry-instrumentation-grpc.gemspec

@@ -42,6 +42,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'grpc-tools', '~> 1.64'
   spec.add_development_dependency 'minitest', '~> 5.0'
   spec.add_development_dependency 'opentelemetry-sdk', '~> 1.1'
+  spec.add_development_dependency 'opentelemetry-test-helpers', '~> 0.4'
+  spec.add_development_dependency 'rake', '~> 13.2'
   spec.add_development_dependency 'rubocop', '~> 1.69.1'
   spec.add_development_dependency 'rubocop-performance', '~> 1.23.0'
   spec.add_development_dependency 'simplecov', '~> 0.17.1'