fix(error-equals): update error equals schemas to have the correct syntax

[Crazyglue]

Here is the syntax for declaring string[] in json schema: https://json-schema.org/understanding-json-schema/reference/array.html

The current definitions before this change would produce a schema that was an array of objects. { [key: string]: any }[] when used with the https://github.com/bcherny/json-schema-to-typescript package

The current schemas dont seem to be used in the repo anywhere, and definitely not in the tests, so this wouldnt have been caught here. However the downstream package asl-types does depend on these schemas, which is where i saw this issue.

I have validated in that package that changing items -> item did in fact fix the conversion process.

Here is the issue created in that package fourTheorem/asl-types#7

And here are the docs for ErrorEquals https://docs.aws.amazon.com/step-functions/latest/dg/concepts-error-handling.html

[codecov]

Codecov Report

Merging #55 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #55   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
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  Files            3         3           
  Lines           41        41           
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  Hits            41        41           

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[ChristopheBougere]

Thank you for the very well detailed bug report and fix @Crazyglue 👌
I just added a test to check that we weren't validating item types on master, and released a v1.7.1