GH-33420: [R] Improve error message when providing a mix of readr and Arrow options

[Rich-T-kid]

Rationale for this change

closes #33420

What changes are included in this PR?

updates the error message returned

Are these changes tested?

No, minimal change so I don't think its needed

Are there any user-facing changes?

better error responses for users.

• GitHub Issue: [R] Improve error message when providing a mix of readr and Arrow options #33420

[github-actions]

Thanks for opening a pull request!

If this is not a minor PR. Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

Then could you also rename the pull request title in the following format?

GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

MINOR: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[Rich-T-kid]

@thisisnic could you take a look at this? 🫡 thx

[thisisnic]

Thanks for the PR @Rich-T-kid! Looks pretty good, just a couple of suggested changes from me:

• please could you update the PR title to include the issue number/name (see other PRs in the repo for examples)
• please could you either add or update any tests for these errors

Give me a shout if you have any question!

[Rich-T-kid]

@thisisnic pushed a PR that updates a test. Could you take another look 😄