Fix bogus return value.

'cppcheck' didn't like the return value:

[src/backend/utils/error/elog.c:983]: (error) Returning pointer to local variable 'outbuf' that will be invalid when returning.

The return value was never used, but let's be tidy.

src/backend/utils/error/elog.c

@@ -969,7 +969,7 @@ errcode_for_socket_access(void)
  * Convert compact error code (ERRCODE_xxx) to 5-char SQLSTATE string,
  * and put it into a 6-char buffer provided by caller.
  */
-char *
+void
 errcode_to_sqlstate(int errcode, char outbuf[6])
 {
 	int	i;
@@ -980,7 +980,6 @@ errcode_to_sqlstate(int errcode, char outbuf[6])
 		errcode >>= 6;
 	}
 	outbuf[5] = '\0';
-	return &outbuf[5];
 }
 
 /*

src/include/utils/elog.h

@@ -202,7 +202,7 @@ extern int	errcode_for_file_access(void);
 extern int	errcode_for_socket_access(void);
 
 extern int sqlstate_to_errcode(const char *sqlstate);
-extern char *errcode_to_sqlstate(int errcode, char outbuf[6]);
+extern void errcode_to_sqlstate(int errcode, char outbuf[6]);
 
 extern int	errmsg(const char *fmt,...) pg_attribute_printf(1, 2);
 extern int	errmsg_internal(const char *fmt,...) pg_attribute_printf(1, 2);