fix: don't reuse ports in courier/SMTP tests

[alnr]

No description provided.

[codecov]

Codecov Report

Merging #3156 (137ac94) into master (b6b1679) will decrease coverage by 0.04%.
The diff coverage is 34.61%.

❗ Current head 137ac94 differs from pull request most recent head 526baa9. Consider uploading reports for the commit 526baa9 to get more accurate results

@@            Coverage Diff             @@
##           master    #3156      +/-   ##
==========================================
- Coverage   77.64%   77.60%   -0.04%     
==========================================
  Files         317      317              
  Lines       19992    20009      +17     
==========================================
+ Hits        15522    15528       +6     
- Misses       3278     3290      +12     
+ Partials     1192     1191       -1     

Impacted Files	Coverage Δ
x/mailhog.go	5.17% <0.00%> (-1.81%)	⬇️
selfservice/flow/settings/test/persistence.go	100.00% <100.00%> (ø)
session/test/persistence.go	100.00% <0.00%> (+0.94%)	⬆️

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