Restclient Instrumentation: Invalid span attribute type Symbol for key 'http.method'

[james-o-johnstone]

Description of the bug

Restclient instrumentation error when using rest-client 1.8.0:

E, [2022-03-19T17:16:18.421864 #632681] ERROR -- : OpenTelemetry error: invalid span attribute value type Symbol for key 'http.method' on span 'HTTP GET'

Share details about your runtime

Operating system details: Linux, Ubuntu 20.04 LTS
RUBY_ENGINE: "ruby"
RUBY_VERSION: "2.5.0"
RUBY_DESCRIPTION: "ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux]"

Share a simplified reproduction if possible

require 'bundler/inline'

gemfile(true) do
  source 'https://rubygems.org'

  gem 'opentelemetry-api'
  gem 'opentelemetry-sdk'
  gem 'opentelemetry-instrumentation-all'
  gem 'rest-client', '1.8.0'
end

require 'opentelemetry-api'
require 'opentelemetry-sdk'
require 'rest-client'

OpenSSL::SSL::SSLContext::DEFAULT_PARAMS[:ciphers]=OpenSSL::SSL::SSLContext.new.ciphers;

OpenTelemetry::SDK.configure do |c|
  c.use_all
end

RestClient::Request.execute(method: :get, url: 'https://www.google.com',
                            timeout: 10)