Fix CHANGELOG.md
Fix CHANGELOG.md

Fix urls about pull request
hamadata/aws-sdk-ruby,takeyuweb/aws-sdk-ruby,aws/aws-sdk-ruby,hamadata/aws-sdk-ruby,hamadata/aws-sdk-ruby,cjyclaire/aws-sdk-ruby,cjyclaire/aws-sdk-ruby,llooker/aws-sdk-ruby,aws/aws-sdk-ruby,takeyuweb/aws-sdk-ruby,llooker/aws-sdk-ruby,aws/aws-sdk-ruby,cjyclaire/aws-sdk-ruby,llooker/aws-sdk-ruby,takeyuweb/aws-sdk-ruby