To apply this via patch before the release of 2.4.9, you will need to apply patches for both the OJS application and for the shared library (in lib/pkp) directly from GitHub:
https://github.com/pkp/ojs/commit/777e16a1dea4f2f3fb1ae536153f2e74c3766a46.diff
https://github.com/pkp/pkp-lib/commit/3e5beea7bdc5d91f52d0d58c8edfe3dbdca910ef.diff
These commits are not part of the current stable 2.4.8 release, so they are not represented in the “recommended patches” diff.
Once successfully applied, you would need to go into the plugin settings and update the settings for ReCAPTCHA v2.