Fix translator notes in comments

The translator comments detailing what a %s inclusion refers to were
accidentally including too many address types.  In practice this is
not a problem since it's not a translated string, but to minimize any
risk of confusion let's fix them anwyays.  Even though this exists in
backbranches there is little use for backpatch as the translation work
has already happened there, so let's avoid the churn.

Author: Japin Li <japinli@hotmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/ME0P300MB04458DE627480614ABE639D2B6FB2@ME0P300MB0445.AUSP300.PROD.OUTLOOK.COM

src/backend/libpq/pqcomm.c

@@ -571,7 +571,7 @@ ListenServerPort(int family, const char *hostName, unsigned short portNumber,
 			{
 				ereport(LOG,
 						(errcode_for_socket_access(),
-				/* translator: third %s is IPv4, IPv6, or Unix */
+				/* translator: third %s is IPv4 or IPv6 */
 						 errmsg("%s(%s) failed for %s address \"%s\": %m",
 								"setsockopt", "SO_REUSEADDR",
 								familyDesc, addrDesc)));
@@ -589,7 +589,7 @@ ListenServerPort(int family, const char *hostName, unsigned short portNumber,
 			{
 				ereport(LOG,
 						(errcode_for_socket_access(),
-				/* translator: third %s is IPv4, IPv6, or Unix */
+				/* translator: third %s is IPv6 */
 						 errmsg("%s(%s) failed for %s address \"%s\": %m",
 								"setsockopt", "IPV6_V6ONLY",
 								familyDesc, addrDesc)));