Fix interceptor eject example in README

The example creates an interceptor using an Axios instance but attempts to eject it using the global axios object. Updated the code to use the correct instance for consistency and clarity.

Summary by cubic

Fix the interceptor eject example to use the created axios instance instead of the global axios object. This prevents confusion and shows the correct way to remove an interceptor from an instance.

Description

• Summary of changes: Updated README to call instance.interceptors.request.eject(myInterceptor) instead of axios.interceptors.request.eject(myInterceptor).
• Reasoning: The interceptor is registered on instance, so ejecting on axios would not remove it and misleads readers.
• Additional context: Docs-only; no runtime changes.

Docs

• Mirror this fix in any code samples on the docs site under /docs/ to keep examples consistent.

Testing

• No tests added; documentation-only change. Tests not needed.

Semantic version impact

• No impact. Docs-only change; no release required.

^{Written for commit 719903e. Summary will update on new commits.}