Remove unused footnote

Author: RebeccaTamachiro

src/content/docs/ssl/reference/certificate-authorities.mdx

@@ -168,6 +168,4 @@ The following table lists the CAA record content for each CA:
 | Google Trust Services | `pki.goog; cansignhttpexchanges=yes`     |
 | SSL.com               | `ssl.com`                                |
 | Sectigo               | `sectigo.com`                            |
-| DigiCert              | `digicert.com; cansignhttpexchanges=yes` |
-
-[^1]: As the IdenTrust cross-sign (DST Root CA X3) expires on **September 30, 2024**, the self-signed ISRG Root X1 will be the only chain used for RSA certificates issued through Let's Encrypt. Refer to [Background](#background) or our [blog](https://blog.cloudflare.com/shortening-lets-encrypt-change-of-trust-no-impact-to-cloudflare-customers) for details.
+| DigiCert              | `digicert.com; cansignhttpexchanges=yes` |