docs: correct Any godoc to reflect true arbitrary-method matching

[hyorimitsu]

Summary

Fixes #3044.

The godoc for Echo.Any() said it only matches a specific set of known HTTP methods and is "not a true catch-any-arbitrary-method" way of matching. That's wrong — Any() registers a single RouteAny route that matches any HTTP method, including ones not known to Echo.

This PR fixes the docs to match the real behavior.

Changes

• echo.go: Rewrite the Any() godoc; note that a method-specific route takes precedence.
• router.go: Fix the AddRouteError comment to use Match() as the example.
• echo_test.go: Add a test that an arbitrary method still matches the RouteAny fallback.

Notes

Docs and test only — no runtime behavior changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.42%. Comparing base (01b45be) to head (87bf4d7).
⚠️ Report is 32 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3046      +/-   ##
==========================================
+ Coverage   93.17%   93.42%   +0.24%     
==========================================
  Files          43       43              
  Lines        4501     4730     +229     
==========================================
+ Hits         4194     4419     +225     
- Misses        189      190       +1     
- Partials      118      121       +3     

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[aldas]

LGTM