Remove line duplicated during conflict resolution.

I included the duplicated ExecTypeFromTL in 578b2297 "Remove WITH OIDS
support".

Reported-By: Peter Eisentraut
Discussion: https://postgr.es/m/ba819888-63c6-7f98-6acb-3731142d9414@2ndquadrant.com

src/backend/executor/execTuples.c

@@ -1604,7 +1604,6 @@ ExecInitResultTypeTL(PlanState *planstate)
 {
 	TupleDesc	tupDesc = ExecTypeFromTL(planstate->plan->targetlist);
 
-	tupDesc = ExecTypeFromTL(planstate->plan->targetlist);
 	planstate->ps_ResultTupleDesc = tupDesc;
 }