Fix openapi-tags-alphabetical rule invalid property declaration

[mdaloia]

Since version 0.9.0 the openapi-tags-alphabetical rule is not working due to a invalid type of its properties attribute (Reference). It must be an array of strings instead of a string. Like this:

- name: openapi-tags-alphabetical
  object: openapi
  description: openapi object should have alphabetical tags
  alphabetical:
    properties:
      - tags
    keyedBy: name

The reason that it stopped working is that in the 0.8.x version from the speecy side there was an adaptation done while the rule was being created.
As on version 0.9.x it relies on oas-linter this code was removed and delegates it to that module, but this adaptation is not present here.

Maybe it is better to add the adaptation and/or a data type validation in oas-linter rules to avoid silent fails (The rule result was always ok because it tried to find in the openapi spec a property whose name was the first letter of the configured property in the rule due to this for).
Let me know if you agree on adding the adaptation in oas-linter, I could open a PR in that case.

[pderaaij]

Looks good to me! Thanks for your contribution!

[pderaaij]

@djtarazona This one can be tagged along as well.