Replace keyserver upload requirement with keys.openpgp.org

The MIT keyserver is frequently unavailable for uploads so it no longer
make sense to block new keys based on its availability.

Once we have main-key signing tooling built into `keyringctl` this
requirement will no longer be necessary since the tooling will be able
to be run from branches already containing the necessary keys.

Signed-off-by: Johannes Löthberg <johannes@kyriasis.com>

.gitlab/issue_templates/New Main Key.md

@@ -51,7 +51,11 @@ merge request to add the new main key can be merged.
   a clearsigned document
 - [ ] The revocation certificate has been sent in an encrypted message to the
   revocation certificate holder
-- [ ] The public key has been uploaded to the pgp.mit.edu and keyserver.ubuntu.com
+- [ ] The public key has been uploaded to the `keyserver.ubuntu.com` and
+  `keys.openpgp.org` keyservers, and the `archlinux.org` UID has been verified
+  on the `keys.openpgp.org` keyserver.  Optionally the key can also be uploaded
+  to the `pgp.mit.edu` keyserver, but this is no longer mandatory as it's
+  frequently flaky.
 - [ ] A merge request to add the new public key has been created
 
 ### Revocation Certificate Holder

.gitlab/issue_templates/New Packager Key.md

@@ -58,7 +58,11 @@ the details section.
   practices](https://gitlab.archlinux.org/archlinux/archlinux-keyring/-/wikis/best-practices#validating-a-key-pair)
 - [ ] The data in the [Details](#details) section is attached to this issue as
   a clearsigned document
-- [ ] The public key has been uploaded to the pgp.mit.edu and keyserver.ubuntu.com
+- [ ] The public key has been uploaded to the `keyserver.ubuntu.com` and
+  `keys.openpgp.org` keyservers, and the `archlinux.org` UID has been verified
+  on the `keys.openpgp.org` keyserver.  Optionally the key can also be uploaded
+  to the `pgp.mit.edu` keyserver, but this is no longer mandatory as it's
+  frequently flaky.
 - [ ] A merge request to add the new public key has been created
 
 ### Main key holders