Don't imply self-signed certs are required

UPGRADE.rst

@@ -51,34 +51,35 @@ returned by the Client-Server API:
 Upgrading to v0.99.0
 ====================
 
-In preparation for Synapse v1.0, you must update your TLS certificates from
-self-signed ones to verifiable ones signed by a trusted root CA.
+In preparation for Synapse v1.0, you must ensure your federation TLS
+certificates are verifiable by signed by a trusted root CA.
 
-If you do not already have a certificate for your domain, the easiest way to get
-one is with Synapse's new ACME support, which will use the ACME protocol to
-provision a certificate automatically. By default, certificates will be obtained
-from the publicly trusted CA Let's Encrypt.
+If you do not already have a valid certificate for your domain, the easiest
+way to get one is with Synapse's new ACME support, which will use the ACME
+protocol to provision a certificate automatically. By default, certificates
+will be obtained from the publicly trusted CA Let's Encrypt.
 
 For a sample configuration, please inspect the new ACME section in the example
 generated config by running the ``generate-config`` executable. For example::
 
   ~/synapse/env3/bin/generate-config
 
-You will need to provide Let's Encrypt (or other ACME provider) access to your
-Synapse ACME challenge responder on port 80, at the domain of your homeserver.
-This requires you either change the port of the ACME listener provided by
-Synapse to a high port and reverse proxy to it, or use a tool like authbind to
-allow Synapse to listen on port 80 without root access. (Do not run Synapse with
-root permissions!)
+You will need to provide Let's Encrypt (or another ACME provider) access to
+your Synapse ACME challenge responder on port 80, at the domain of your
+homeserver. This requires you to either change the port of the ACME listener
+provided by Synapse to a high port and reverse proxy to it, or use a tool
+like ``authbind`` to allow Synapse to listen on port 80 without root access.
+(Do not run Synapse with root permissions!)
 
-You will need to back up or delete your self signed TLS certificate
-(``example.com.tls.crt`` and ``example.com.tls.key``), Synapse's ACME
-implementation will not overwrite them.
+If you are already using self-signed ceritifcates, you will need to back up
+or delete them (files ``example.com.tls.crt`` and ``example.com.tls.key`` in
+Synapse's root directory), Synapse's ACME implementation will not overwrite
+them.
 
 You may wish to use alternate methods such as Certbot to obtain a certificate
 from Let's Encrypt, depending on your server configuration. Of course, if you
 already have a valid certificate for your homeserver's domain, that can be
-placed in Synapse's config directory without the need for ACME.
+placed in Synapse's config directory without the need for any ACME setup.
 
 Upgrading to v0.34.0
 ====================