Delete digicert-update folder and add redirects

Author: RebeccaTamachiro

public/_redirects

@@ -1021,6 +1021,7 @@
 /ssl/reference/cipher-suites/custom-certificates/ /ssl/edge-certificates/custom-certificates/#certificate-packs 301
 /ssl/reference/cipher-suites/matching-on-origin/ /ssl/origin-configuration/cipher-suites/#match-on-origin 301
 /ssl/reference/migration-guides/lets-encrypt-chain/ /ssl/reference/certificate-authorities/#lets-encrypt 301
+/ssl/reference/migration-guides/digicert-update/ /ssl/reference/migration-guides/ 301
 /ssl/reference/validation-backoff-schedule/ /ssl/edge-certificates/changing-dcv-method/validation-backoff-schedule/ 301
 /ssl/universal-ssl/changing-dcv-method/ /ssl/edge-certificates/changing-dcv-method/ 301
 /support/dns/how-to/certification-authority-authorization-caa-faq/ /ssl/edge-certificates/troubleshooting/caa-records/ 301
@@ -1791,6 +1792,7 @@
 /rules/url-forwarding/dynamic-redirects/* /rules/url-forwarding/single-redirects/:splat 301
 /ssl/ssl-tls/* /ssl/reference/:splat 301
 /ssl/reference/cipher-suites/* /ssl/edge-certificates/additional-options/cipher-suites/:splat 301
+/ssl/reference/migration-guides/digicert-update/* /ssl/reference/migration-guides/ 301
 /support/account-management-billing/billing-cloudflare-add-on-services/* https://www.cloudflare.com/plans/ 301
 /tenant/tutorial/* /tenant/get-started/ 301
 /waf/managed-rulesets/* /waf/managed-rules/:splat 301