Raise a validation exception if the responses section in an openApi definition path is not a dictionary object

[moelasmar]

Issue #, if available:

Description of changes:

Description of how you validated changes:

Checklist:

• Add/update tests using:
  • Correct values
  • Bad/wrong values (None, empty, wrong type, length, etc.)
  • Intrinsic Functions
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected

Examples?

Please reach out in the comments, if you want to add an example. Examples will be
added to sam init through https://github.com/awslabs/aws-sam-cli-app-templates/

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

[codecov-commenter]

Codecov Report

Merging #2214 (37ca8f4) into develop (e7a1496) will increase coverage by 0.88%.
The diff coverage is 98.38%.

@@             Coverage Diff             @@
##           develop    #2214      +/-   ##
===========================================
+ Coverage    93.58%   94.46%   +0.88%     
===========================================
  Files           90       95       +5     
  Lines         6124     6563     +439     
  Branches      1260     1326      +66     
===========================================
+ Hits          5731     6200     +469     
+ Misses         183      168      -15     
+ Partials       210      195      -15     

Impacted Files	Coverage Δ
samtranslator/model/lambda_.py	93.10% <ø> (ø)
samtranslator/plugins/globals/globals.py	99.05% <ø> (ø)
samtranslator/translator/logical_id_generator.py	100.00% <ø> (+9.09%)	⬆️
samtranslator/region_configuration.py	77.77% <63.63%> (-22.23%)	⬇️
samtranslator/translator/translator.py	97.26% <90.00%> (+0.07%)	⬆️
samtranslator/swagger/swagger.py	94.00% <92.68%> (+0.63%)	⬆️
samtranslator/__init__.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/dialup.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/feature_toggle.py	100.00% <100.00%> (+12.16%)	⬆️
samtranslator/intrinsics/actions.py	98.75% <100.00%> (+0.03%)	⬆️
... and 36 more

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