Documentation: Clarify current test recorder version in testing guide

[jeremymeng]

Issue Description

The documentation in Quickstart-on-how-to-write-tests.md contains inconsistent and unclear information about which version of @azure-tools/test-recorder is currently recommended.

Current Problems

1. Line 38 states: "This quickstart is based on 3.x.y version of recorder tool"
2. Line 146 mentions: "Eventually, all the tests will be migrated to depend on the 4.m.n version"
3. The migration guide link references "recorder v4" but it's unclear if this migration is complete or ongoing

Impact

Developers following the quickstart guide are unclear about:

• Which recorder version they should use for new packages
• Whether version 3.x.y or 4.m.n is the current standard
• If they need to plan for migration

Requested Changes

1. Update the documentation to clearly state the current recommended recorder version
2. If migration to v4 is complete, remove references to v3
3. If migration is still in progress:
   • Clearly indicate which version to use for new projects
   • Provide timeline or status for the migration
   • Add clear guidance on when to use each version

Files Affected

• documentation/Quickstart-on-how-to-write-tests.md

Related Documentation

• test-recorder README
• Asset Sync Workflow Migration Guide