perf(share/shwap/p2p/shrex): Increase default concurrency limit for shrex server to 32

[renaynay]

Will do some further testing on this first, so in draft mode for now, but this feels like a reasonable req limit.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 44.86%. Comparing base (2469e7a) to head (7579ec9).
Report is 449 commits behind head on main.

Files with missing lines	Patch %	Lines
share/shwap/p2p/shrex/params.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4141      +/-   ##
==========================================
+ Coverage   44.83%   44.86%   +0.02%     
==========================================
  Files         265      309      +44     
  Lines       14620    22701    +8081     
==========================================
+ Hits         6555    10184    +3629     
- Misses       7313    11434    +4121     
- Partials      752     1083     +331     

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