Remove trailing commas from enums.

Buildfarm member mylodon doesn't like them.  Actually, I don't like
them either, but I failed to notice these before pushing commit
6f3bd98e.

src/include/pgstat.h

@@ -746,7 +746,7 @@ typedef enum
 	WAIT_EVENT_SYSLOGGER_MAIN,
 	WAIT_EVENT_WAL_RECEIVER_MAIN,
 	WAIT_EVENT_WAL_SENDER_MAIN,
-	WAIT_EVENT_WAL_WRITER_MAIN,
+	WAIT_EVENT_WAL_WRITER_MAIN
 } WaitEventActivity;
 
 /* ----------
@@ -764,7 +764,7 @@ typedef enum
 	WAIT_EVENT_SSL_OPEN_SERVER,
 	WAIT_EVENT_WAL_RECEIVER_WAIT_START,
 	WAIT_EVENT_WAL_SENDER_WAIT_WAL,
-	WAIT_EVENT_WAL_SENDER_WRITE_DATA,
+	WAIT_EVENT_WAL_SENDER_WRITE_DATA
 } WaitEventClient;
 
 /* ----------