fix(ci): update fake_peer_set test to avoid spurious failures

[arya2]

Motivation

This test may still be unreliable due to timing issues if the transactions are being rejected because there is a second request in the mempool_requests_for_transactions for the same data that might also receive Nil.

Related to #5384.

Solution

• Move mempool.enable() below peer_set.expect_request().await to wait for the second chain tip change

Review

Anyone can review.

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?
• How do you know it works? Does it have tests?

[teor2345]

@arya2 can you please add a priority to this PR? Thanks!

[codecov]

Codecov Report

Merging #5758 (fb0d312) into main (f573365) will decrease coverage by 0.10%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5758      +/-   ##
==========================================
- Coverage   78.69%   78.59%   -0.11%     
==========================================
  Files         306      306              
  Lines       38687    38687              
==========================================
- Hits        30445    30406      -39     
- Misses       8242     8281      +39     

[teor2345]

Thanks, let's see if it works!