remove check for nested intrinsic functions

[shadycuz]

This feature was based on the nested function limitations in the AWS CloudFormation documentation. However, in turns out that the AWS documentation is incorrect and nested functions are allowed in many places where the documentation says they are not. Since this feature was doing more harm than good, it has been removed.

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.58%. Comparing base (f1b9d72) to head (5c96f8f).
Report is 122 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/cloud_radar/cf/unit/_template.py	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #422      +/-   ##
===========================================
- Coverage    95.00%   94.58%   -0.42%     
===========================================
  Files           11       12       +1     
  Lines          760      850      +90     
  Branches       155      160       +5     
===========================================
+ Hits           722      804      +82     
- Misses          21       25       +4     
- Partials        17       21       +4     

Flag	Coverage Δ
unit	94.58% <94.73%> (-0.42%)	⬇️

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[dhutchison]

Just to confirm what I'd wondered about in the other thread - it does appear cfn-lint has support for checking intrinsic function nesting now - so def believe people should be relying on the linter for this check instead of this testing library. Example definition is here.

[dhutchison]

Changes look good to me 👍🏻