docs: replace 'Basic' with 'Bearer' auth in quick start

Author: childish-sambino

README.md

@@ -56,7 +56,7 @@ gem install ruby_http_client
 
 ```ruby
 require 'ruby_http_client'
-global_headers = {'Authorization' => 'Basic XXXXXXX' }
+global_headers = {'Authorization' => 'Bearer XXXXXXX' }
 client = SendGrid::Client.new(host: 'base_url', request_headers: global_headers)
 client.your.api._(param).call.get
 puts response.status_code
@@ -68,7 +68,7 @@ puts response.headers
 
 ```ruby
 require 'ruby_http_client'
-global_headers = {'Authorization' => 'Basic XXXXXXX' }
+global_headers = {'Authorization' => 'Bearer XXXXXXX' }
 client = SendGrid::Client.new(host: 'base_url', request_headers: global_headers)
 query_params = { 'hello' => 0, 'world' => 1 }
 request_headers = { 'X-Test' => 'test' }