ReCAPTCHA proxy is misconfigured

[ctgraham]

Describe the bug
3.3 changes the config.inc.php proxy settings and Guzzle, without touching ReCAPTCHA's usage.

To Reproduce
Steps to reproduce the behavior:

1. Configure 3.3 with new proxy settings
2. Enable and attempt ReCAPTCHA
3. ReCAPTCHA uses old (non-existent) proxy settings

https://forum.pkp.sfu.ca/t/you-did-not-pass-the-validation-check-used-to-prevent-spam-submissions/48023/34?u=ctgraham

What application are you using?
OJS 3.3.0-6

Additional information
#6539 updates ReCAPTCHA to use new proxy settings (courtesy of Guzzle) in 3.4

[NateWr]

cc @jonasraoni and @asmecher It looks like part of #6539 needs to be back ported for 3.3.

[asmecher]

This should be resolved by #7226, which tests fine locally (without proxy) -- but I'd love confirmation that it resolves the issue in a proxy scenario too.