Bump Yosys dependency to >=0.40

[whitequark]

No description provided.

[codecov]

Codecov Report

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

Project coverage is 89.86%. Comparing base (b36e7e0) to head (9d780f1).

Files	Patch %	Lines
amaranth/back/verilog.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1309      +/-   ##
==========================================
- Coverage   89.94%   89.86%   -0.08%     
==========================================
  Files          44       44              
  Lines       10647    10647              
  Branches     2595     2308     -287     
==========================================
- Hits         9576     9568       -8     
- Misses        882      885       +3     
- Partials      189      194       +5     

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