Correct a comment on logtape.c's leader tape.

randomAccess parallel tuplesorts are disallowed because the leader would
try to write to its own leader tape, not because the leader would try to
write to a worker tape directly.

Cleanup from commit 9da0cc35.

src/backend/utils/sort/logtape.c

@@ -471,7 +471,7 @@ ltsConcatWorkerTapes(LogicalTapeSet *lts, TapeShare *shared,
 	 * Compute number of hole blocks so that we can later work backwards, and
 	 * instrument number of physical blocks.  We don't simply use physical
 	 * blocks directly for instrumentation because this would break if we ever
-	 * subsequently wrote to worker tape.
+	 * subsequently wrote to the leader tape.
 	 *
 	 * Working backwards like this keeps our options open.  If shared BufFiles
 	 * ever support being written to post-export, logtape.c can automatically