Remove some more useless assignments.

Found with clang's scan-build tool.  It also whines about a lot of
other dead stores that we should *not* change IMO, either as a matter
of style or future-proofing.  But these places seem like clear
oversights.

Discussion: https://postgr.es/m/CAEudQAo1+AcGppxDSg8k+zF4+Kv+eJyqzEDdbpDg58-=MQcerQ@mail.gmail.com

src/backend/parser/parse_utilcmd.c

@@ -1765,7 +1765,6 @@ generateClonedIndexStmt(RangeVar *heapRel, Relation source_idx,
 			char	   *attname;
 
 			attname = get_attname(indrelid, attnum, false);
-			keycoltype = get_atttype(indrelid, attnum);
 
 			iparam->name = attname;
 			iparam->expr = NULL;