[doc][elixir] remove hard-coded refs to openapipetstore

[efcasado]

Description

Generated documentation in the Connection module includes hard-coded references to the sample OpenAPIPetstore application.

This PR includes a fix to replace these hard-coded references by dynamic references to the generated module.

@mrmstn, @wing328 - This should be an easy one. As usual, curious to hear your thoughts 😊

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
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  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
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[wing328]

lgtm. thanks fo the fix