Fix nn.Module typing.

[copybara-service]

Fix nn.Module typing.

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[codecov-commenter]

Codecov Report

Merging #3289 (c754748) into main (9e82cdb) will decrease coverage by 0.02%.
The diff coverage is 40.00%.

@@            Coverage Diff             @@
##             main    #3289      +/-   ##
==========================================
- Coverage   82.61%   82.60%   -0.02%     
==========================================
  Files          55       55              
  Lines        6317     6319       +2     
==========================================
+ Hits         5219     5220       +1     
- Misses       1098     1099       +1     

Files Changed	Coverage Δ
flax/linen/module.py	92.02% <40.00%> (-0.11%)	⬇️