[1.x] fix: prevent google/recaptcha from updating to v1.5 or later

[dsevillamartin]

v1.3 is the latest for PHP 8.3, but PHP 8.4 supports the latter, and v1.5 has breaking changes that give a Fatal notice error.

Changes proposed in this pull request:
google/recaptcha v1.5 introduces breaking changes. Hard to catch since v1.4 and later require PHP 8.4+.

Fatal error: Declaration of FoF\ReCaptcha\ReCaptcha\GuzzleRequestMethod::submit(ReCaptcha\RequestParameters $params) must be compatible with ReCaptcha\RequestMethod::submit(ReCaptcha\RequestParameters $params): string in <FLARUM>\fof-recaptcha\src\ReCaptcha\GuzzleRequestMethod.php on line 36

Reviewers should focus on:

Screenshot

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).