psql: Remove one use of HAVE_UNIX_SOCKETS

This use was not protecting any unportable code, it was just omitting
the code because it wouldn't be used.  Remove the use to reduce code
complexity a bit.

Discussion: https://www.postgresql.org/message-id/flat/54bde68c-d134-4eb8-5bd3-8af33b72a010@2ndquadrant.com

src/bin/psql/prompt.c

@@ -12,11 +12,6 @@
 #include <win32.h>
 #endif
 
-#ifdef HAVE_UNIX_SOCKETS
-#include <unistd.h>
-#include <netdb.h>
-#endif
-
 #include "common.h"
 #include "common/string.h"
 #include "input.h"
@@ -147,7 +142,6 @@ get_prompt(promptStatus_t status, ConditionalStack cstack)
 							if (*p == 'm')
 								buf[strcspn(buf, ".")] = '\0';
 						}
-#ifdef HAVE_UNIX_SOCKETS
 						/* UNIX socket */
 						else
 						{
@@ -158,7 +152,6 @@ get_prompt(promptStatus_t status, ConditionalStack cstack)
 							else
 								snprintf(buf, sizeof(buf), "[local:%s]", host);
 						}
-#endif
 					}
 					break;
 					/* DB server port number */