docs(response-interceptor.md): improve example

[bangank36]

Description

• Update Text replacement example for Response Interceptor

Motivation and Context

• In the Replace text and change http status code example, changing Hello to Teapot won't show anything since there is no Hello string in http://www.example.com
• Suggest to update string Example, also should use replaceAll since the Example is in the document title as well, so it maybe hard to notice the change

How has this been tested?

• Run an express app with target http://www.example.com
• Make sure the word Example is changed Hello

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.

[coveralls]

Coverage: 97.872%. Remained the same when pulling 767917b7fa2ea31efe24dc5f5b5c808ee79edda6 on bangank36:patch-1 into 47b7e018f614bcdc06f72c4fdbac3a91ba3b5bb7 on chimurai:master.

[chimurai]

Thanks!