update env variables guide

Author: bahmutov

README.md

@@ -98,7 +98,7 @@ package = "netlify-plugin-cypress"
 
 See [cypress-example-kitchensink](https://github.com/cypress-io/cypress-example-kitchensink) and recorded results at [![Cypress Dashboard](https://img.shields.io/badge/cypress-dashboard-brightgreen.svg)](https://dashboard.cypress.io/#/projects/4b7344/runs)
 
-**Security note 🔐:** you should keep your `CYPRESS_RECORD_KEY` secret. Keep an eye on [this Netlify question](https://community.netlify.com/t/common-issue-using-environment-variables-on-netlify-correctly/267); we really hope Netlify hides this variable in logs if accidentally exposed and does not pass the environment variables to forked pull requests.
+**Security note 🔐:** you should keep your `CYPRESS_RECORD_KEY` secret. You can control how Netlify builds external pull requests, see [the doc](https://docs.netlify.com/configure-builds/environment-variables/) - you never want to expose sensitive environment variables to outside builds.
 
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