fix: handle dynamics in map literals for avoid-dynamic

[incendial]

Please write a short comment explaining your change (or "none" for internal only changes)

#1191

[codecov]

Codecov Report

Merging #1194 (6cd6b17) into master (85be501) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 6cd6b17 differs from pull request most recent head 7d3f0ad. Consider uploading reports for the commit 7d3f0ad to get more accurate results

@@           Coverage Diff           @@
##           master    #1194   +/-   ##
=======================================
  Coverage   86.29%   86.29%           
=======================================
  Files         363      363           
  Lines        8179     8182    +3     
=======================================
+ Hits         7058     7061    +3     
  Misses       1121     1121           

Impacted Files	Coverage Δ
...les_list/avoid_ignoring_return_values/visitor.dart	96.96% <ø> (ø)
...k_for_equals_in_render_object_setters/visitor.dart	97.43% <ø> (ø)
.../rules_list/prefer_moving_to_variable/visitor.dart	100.00% <ø> (ø)
.../anti_patterns/anti_patterns_list/long_method.dart	100.00% <100.00%> (ø)
...tterns/anti_patterns_list/long_parameter_list.dart	100.00% <100.00%> (ø)
...alyzer/rules/rules_list/avoid_dynamic/visitor.dart	100.00% <100.00%> (ø)

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