The PQ cannot handle the prune mode change correctly

[Rustin170506]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Create a partitioned table.
2. Insert a lot of data(more than 1000 rows)
3. Change the prune mode
4. The PQ will still use the dynamic pattern to analyze the table

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

Use the static prune mode to analyze the table.

3. What did you see instead (Required)

The PQ will still use the dynamic pattern to analyze the table

4. What is your TiDB version? (Required)

release-8.5, master