add intro note about downloads being disabled (#18499)

Author: bwestover

data/release-notes/2-21/17.yml

@@ -1,4 +1,5 @@
 date: '2021-03-23'
+intro: Downloads have been disabled due to a major bug affecting multiple customers. A fix will be available in the next patch.
 sections:
   security_fixes:
     - '**HIGH:** A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. User-controlled configuration options used by GitHub Pages were not sufficiently restricted and made it possible to override environment variables leading to code execution on the GitHub Enterprise Server instance. To exploit this vulnerability, an attacker would need permission to create and build a GitHub Pages site on the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.0.3 and was fixed in 3.0.3, 2.22.9, and 2.21.17. This vulnerability was reported via the GitHub Bug Bounty program and has been assigned CVE-2021-22864.'

data/release-notes/2-22/9.yml

@@ -1,4 +1,5 @@
 date: '2021-03-23'
+intro: Downloads have been disabled due to a major bug affecting multiple customers. A fix will be available in the next patch.
 sections:
   security_fixes:
     - '**HIGH:** A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. User-controlled configuration options used by GitHub Pages were not sufficiently restricted and made it possible to override environment variables leading to code execution on the GitHub Enterprise Server instance. To exploit this vulnerability, an attacker would need permission to create and build a GitHub Pages site on the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.0.3 and was fixed in 3.0.3, 2.22.9, and 2.21.17. This vulnerability was reported via the GitHub Bug Bounty program and has been assigned CVE-2021-22864.'

data/release-notes/3-0/3.yml

@@ -1,5 +1,5 @@
 date: '2021-03-23'
-intro: The minimum infrastructure requirements have increased for {% data variables.product.prodname_ghe_server %} 3.0+. For more information, see "[About minimum requirements for GitHub Enterprise Server 3.0 and later](/admin/enterprise-management/upgrading-github-enterprise-server#about-minimum-requirements-for-github-enterprise-server-30-and-later)."
+intro: Downloads have been disabled due to a major bug affecting multiple customers. A fix will be available in the next patch.
 sections:
   security_fixes:
     - '**HIGH:** A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. User-controlled configuration options used by GitHub Pages were not sufficiently restricted and made it possible to override environment variables leading to code execution on the GitHub Enterprise Server instance. To exploit this vulnerability, an attacker would need permission to create and build a GitHub Pages site on the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.0.3 and was fixed in 3.0.3, 2.22.9, and 2.21.17. This vulnerability was reported via the GitHub Bug Bounty program and has been assigned CVE-2021-22864.'