Fix do not track nested reactivity in map_keyed/map_indexed

[lukechu10]

Fixes #739 but not #741

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.92%. Comparing base (7e58231) to head (4e924b7).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/sycamore-reactive/src/utils.rs	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #742      +/-   ##
==========================================
+ Coverage   72.65%   72.92%   +0.26%     
==========================================
  Files          44       44              
  Lines        6378     6400      +22     
==========================================
+ Hits         4634     4667      +33     
+ Misses       1744     1733      -11     

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