bootstrap version is not correctly incremented

[morgo]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

From code inspection of bootstrap.go, I can see a bug introduced in #33094

Version 85 is introduced, but the currentBootstrapVersion is still on version 84:

tidb/session/bootstrap.go

Lines 588 to 590 in c4fbc8e

	// currentBootstrapVersion is defined as a variable, so we can modify its value for testing.
	// please make sure this is the largest version
	var currentBootstrapVersion int64 = version84

Without this, the code won't run.

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

version 85.

4. What is your TiDB version? (Required)

master