Reverts #10866

Summary by cubic

Reverts support for passing a URL object to axios(url) and config.url. v1.x now accepts string URLs only to match prior behavior.

Description

• Summary of changes
  • Removed URL-object handling and normalization in core request flow.
  • Reverted types to string for AxiosRequestConfig.url and method overloads in index.d.ts/index.d.cts.
  • Updated README to remove URL object examples.
  • Deleted tests that validated URL object support.
• Reasoning
  • Restore pre-fix: support URL object as config.url input #10866 behavior in v1.x to avoid an API change and keep types/runtime consistent.
• Additional context
  • Migration: replace new URL(...) inputs with url.toString() or a string literal.

Docs

• Update /docs/ to state that config.url and axios(url, config) accept a string URL only. Remove any URL object examples.

Testing

• Removed tests related to URL object handling in API, adapter, and helper suites.
• No new tests added; existing string-based URL coverage remains. No additional tests needed.

Semantic version impact

• Patch: reverts an unintended behavior change in v1.x and restores the original, documented API.

^{Written for commit 5a15ef6. Summary will update on new commits.}