May be a typo in optimizer's cost formula

[winoros]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

From the comment, it seems that the tableRows is used to calculate the final network cost of the TableReader side.
So it should use getCardinality(p.tablePlan, ....) as its value.

But in the current codebase, we set it to getCardinality(p.indexPlan, ...).
This could be a typo.

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

current master.

[time-and-fate]

Also mentioned in #45077 (comment)