Gravity Forms 2.8.9

- Updated recommended minimum PHP version on the System Status page to 7.3, matching the WordPress recommendation.
- Updated minimum WordPress version on the System Status page to 5.3.
- Updated the gravityforms.php examples for defining the reCAPTCHA constants: [GF_RECAPTCHA_PRIVATE_KEY](https://docs.gravityforms.com/gf_recaptcha_private_key/) and [GF_RECAPTCHA_PUBLIC_KEY](https://docs.gravityforms.com/gf_recaptcha_public_key/).

- Fixed an issue where PHP notice thrown when a payment add-on failed without providing proper error messages.
- Fixed submissions which fail honeypot validation or are marked as spam using the configured confirmation. The default "Thanks for contacting us! We will get in touch with you shortly." message will be used instead.

- Added security enhancements.