chore(deps): update dependencies

[bhdnb]

Summary

Updates the locked dependencies and adds support for Guzzle 8.

Guzzle 8 no longer uppercases the HTTP method, and the API classes pass it
lowercase ('get', 'post', 'patch', ...). With Guzzle 8 installed, every
request sent through GuzzleHttpClient was rejected by the Crowdin API with
400 Bad Request. The client now uppercases the method before building the
request, which is a no-op on Guzzle 6 and 7.

Only users who opt into the Guzzle handler ('http_client_handler' => 'guzzle'
or a GuzzleHttpClient instance) are affected; the default cURL handler
already uppercased the method.

Changes

• composer.json: allow guzzlehttp/guzzle ^8 (now ^6.2 || ^7 || ^8).
• GuzzleHttpClient::request(): strtoupper($method).
• GuzzleHttpClientTest: new test asserting the method sent on the wire,
  using Guzzle's MockHandler.
• composer.lock: refreshed all dependencies and moved to Guzzle 8 so CI
  exercises the new major.

Package	Before	After
guzzlehttp/guzzle	7.8.1	8.2.0
guzzlehttp/psr7	2.6.2	3.1.0
guzzlehttp/promises	2.0.2	3.0.2
phpunit/phpunit	9.6.15	9.6.37
friendsofphp/php-cs-fixer	3.45.0	3.95.27

composer audit went from 15 advisories (Guzzle, PSR-7, PHPUnit,
symfony/process) to none.

Notes

• No public API changes; backward compatible.
• Composer 2.10+ refuses to install Guzzle 6 by default because of unfixed
  security advisories, so ^6.2 is kept only for existing installs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.21%. Comparing base (d96d4d9) to head (7f986ce).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #286      +/-   ##
============================================
+ Coverage     95.10%   95.21%   +0.11%     
  Complexity     2540     2540              
============================================
  Files           217      217              
  Lines          6959     6959              
============================================
+ Hits           6618     6625       +7     
+ Misses          341      334       -7     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.