Increase ZIP-401 mempool cost thresholds for Orchard transactions

[teor2345]

Motivation

This PR changes Zebra's mempool cost thresholds to match zcashd 5.5.0, as specified in the latest ZIP-401 update:
https://github.com/zcash/zips/pull/685/files#diff-e8ce48f91a8494325daeea2a8bfb2f5a4f1d6d261d0c3a985da463b03a24e14cR82

This is a standard rule, so it is not consensus-critical.

Solution

Update the mempool cost threshold constants to match ZIP-401 and zcashd

Review

This is a routine change.

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 #6521 (0da6b5f) into main (2e434b0) will decrease coverage by 0.09%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6521      +/-   ##
==========================================
- Coverage   77.68%   77.59%   -0.09%     
==========================================
  Files         305      305              
  Lines       40104    40104              
==========================================
- Hits        31154    31119      -35     
- Misses       8950     8985      +35     

[arya2]

This looks good, thank you!

(Please add updating the comment to follow-up work if this merges as-is)