fix: allow intrinsics in NotificationARNs property

[keetonian]

Issue #, if available:
#1087

Description of changes:
Allow !Ref and other intrinsics in NotificationARNs property of a Serverless::Application.

Description of how you validated changes:
Tests updated and pass. Deployed a template with desired changes.

Checklist:

• Write/update tests
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #1088 into develop will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           develop    #1088   +/-   ##
========================================
  Coverage    94.93%   94.93%           
========================================
  Files           69       69           
  Lines         3377     3377           
  Branches       663      663           
========================================
  Hits          3206     3206           
  Misses          89       89           
  Partials        82       82

Impacted Files	Coverage Δ
samtranslator/model/sam_resources.py	95.49% <ø> (ø)	⬆️
samtranslator/model/cloudformation.py	85.71% <100%> (ø)	⬆️

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[jlhood]

Nice. Thanks for fixing. Just to confirm: this allows any intrinsic, not just Ref, right?

[keetonian]

Correct, any intrinsic