Fix incorrect comment in preptlist.c

Author: Etsuro Fujita
Reviewed-by: Richard Guo, Tom Lane
Discussion: https://postgr.es/m/CAPmGK15V8dcVxL9vcgVWPHV6pw1qzM42LzoUkQDB7-e+1onnJw@mail.gmail.com

src/backend/optimizer/prep/preptlist.c

@@ -12,7 +12,7 @@
  * For UPDATE and DELETE queries, the targetlist must also contain "junk"
  * tlist entries needed to allow the executor to identify the rows to be
  * updated or deleted; for example, the ctid of a heap row.  (The planner
- * adds these; they're not in what we receive from the planner/rewriter.)
+ * adds these; they're not in what we receive from the parser/rewriter.)
  *
  * For all query types, there can be additional junk tlist entries, such as
  * sort keys, Vars needed for a RETURNING list, and row ID information needed