Fix use-after-free with multirange types in CREATE TYPE

The code was freeing the name of the multirange type function stored in
the parse tree but it should not do that.  Event triggers could for
example look at such a corrupted parsed tree with a ddl_command_end
event.

Author: Alex Kozhemyakin, Sergey Shinderuk
Reviewed-by: Peter Eisentraut, Michael Paquier
Discussion: https://postgr.es/m/d5042d46-b9cd-6efb-219a-71ed0cf45bc8@postgrespro.ru
Backpatch-through: 14

src/backend/commands/typecmds.c

@@ -1707,7 +1707,6 @@ DefineRange(ParseState *pstate, CreateRangeStmt *stmt)
 	/* Create cast from the range type to its multirange type */
 	CastCreate(typoid, multirangeOid, castFuncOid, 'e', 'f', DEPENDENCY_INTERNAL);
 
-	pfree(multirangeTypeName);
 	pfree(multirangeArrayName);
 
 	return address;