Docs - Remove references to RadfishAPIService

[theangchen]

• Patterns - Integrating with Backend Services:
• Remove references to RadfishAPIService.
• Replace with documentation for fetch (suggested link to MDN documentation).
• Remove RADFishAPIService from the Making API Requests section in boilerplate README. Replace with fetch documentation from MDN
• Will also need to update mock-api example

If it's in code, replace with fetch. If its in documentation, just remove it. No need to document fetch.