fix(testnet): Increase legacy chain limit to 100,000

[teor2345]

Motivation

I just restarted my testnet instance, and it has been 10,000 blocks without a v5 transaction. So we need to increase the limit again.

Ticket #5912 will make this check partly redundant, because it will verify all the checkpoints to make sure we are on the correct chain.

Solution

Just increase the constant for the number of blocks.

Review

This is a low priority testnet fix.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

[codecov]

Codecov Report

Merging #6053 (9357a94) into main (e20cf95) will increase coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6053      +/-   ##
==========================================
+ Coverage   78.25%   78.27%   +0.01%     
==========================================
  Files         312      312              
  Lines       39418    39418              
==========================================
+ Hits        30846    30853       +7     
+ Misses       8572     8565       -7