Closes #2405 update messaging for duplicates in derive_extreme_event()

[jeffreyad]

Thank you for your Pull Request! We have developed this task checklist from the Development Process Guide to help with the final steps of the process. Completing the below tasks helps to ensure our reviewers can maximize their time on your code as well as making sure the admiral codebase remains robust and consistent.

Please check off each taskbox as an acknowledgment that you completed the task or check off that it is not relevant to your Pull Request. This checklist is part of the Github Action workflows and the Pull Request will not be merged into the main branch until you have checked off each task.

• [x] Place Closes # into the beginning of your Pull Request Title (Use Edit button in top-right if you need to update)
• [x] Code is formatted according to the tidyverse style guide. Run styler::style_file() to style R and Rmd files
• [x] Updated relevant unit tests or have written new unit tests, which should consider realistic data scenarios and edge cases, e.g. empty datasets, errors, boundary cases etc. - See Unit Test Guide
• [x] If you removed/replaced any function and/or function parameters, did you fully follow the deprecation guidance?
• [x] Review the Cheat Sheet. Make any required updates to it by editing the file inst/cheatsheet/admiral_cheatsheet.pptx and re-upload a PDF version of it to the same folder.
• [x] Update to all relevant roxygen headers and examples, including keywords and families. Refer to the categorization of functions to tag appropriate keyword/family.
• [x] Run devtools::document() so all .Rd files in the man folder and the NAMESPACE file in the project root are updated appropriately
• [x] Address any updates needed for vignettes and/or templates
• [x] Update NEWS.md under the header # admiral (development version) if the changes pertain to a user-facing function (i.e. it has an @export tag) or documentation aimed at users (rather than developers). A Developer Notes section is available in NEWS.md for tracking developer-facing issues.
• [x] Build admiral site pkgdown::build_site() and check that all affected examples are displayed correctly and that all new functions occur on the "Reference" page.
• [x] Address or fix all lintr warnings and errors - lintr::lint_package()
• [x] Run R CMD check locally and address all errors and warnings - devtools::check()
• [x] Link the issue in the Development Section on the right hand side.
• [x] Address all merge conflicts and resolve appropriately
• [x] Pat yourself on the back for a job well done! Much love to your accomplishment!

[jeffreyad]

@bundfussr I don't think this does everything we wanted, but it may be step in the right direction.

[github-actions[bot]]

Package	Line Rate	Health
admiral	96%	✔
Summary	96% (4822 / 5017)	✔

[bms63]

@bundfussr if you have time, please check this one. If not not we can save for 1.2 release.

@jeffreyad can we add some tests around these messages if we go forward? If you don't have time, maybe we should definitely wait until 1.2 release

[bms63]

@jeffreyad do you have time today to finish updates? If not, we can just push to 1.2!! You have done enough !! :)