Remove unnecessary include

autovacuum.c no longer needs dsa.h, since commit 31ae1638.
Author: Masahiko Sawada
Discussion: https://postgr.es/m/CAD21AoCWvYyXrvdANSHWWWEWJH5TeAWAkJ_2gqrHhukG+OBo1g@mail.gmail.com

src/backend/postmaster/autovacuum.c

@@ -94,7 +94,6 @@
 #include "storage/sinvaladt.h"
 #include "storage/smgr.h"
 #include "tcop/tcopprot.h"
-#include "utils/dsa.h"
 #include "utils/fmgroids.h"
 #include "utils/fmgrprotos.h"
 #include "utils/lsyscache.h"