Remove mention of default port with SRV records (#1615)

changelogs/server_server/newsfragments/1615.clarification

@@ -0,0 +1 @@
+Remove spurious mention of a "default port" with respect to SRV record lookup.

content/server-server-api.md

@@ -162,13 +162,12 @@ to send. The process overall is as follows:
         `<delegated_hostname>`. The target server must present a valid
         certificate for `<delegated_hostname>`.
 
-4.  If the `/.well-known` request resulted in an error response, a
-    server is found by resolving an SRV record for
-    `_matrix._tcp.<hostname>`. This may result in a hostname (to be
-    resolved using AAAA or A records) and port. Requests are made to the
-    resolved IP address and port, using 8448 as a default port, with a
-    `Host` header of `<hostname>`. The target server must present a
-    valid certificate for `<hostname>`.
+4.  If the `/.well-known` request resulted in an error response, a server is
+    found by resolving an SRV record for `_matrix._tcp.<hostname>`. This may
+    result in a hostname (to be resolved using AAAA or A records) and
+    port. Requests are made to the resolved IP address and port, with a `Host`
+    header of `<hostname>`. The target server must present a valid certificate
+    for `<hostname>`.
 
 5.  If the `/.well-known` request returned an error response, and the
     SRV record was not found, an IP address is resolved using CNAME, AAAA and A