ICU-23293 Remove attribute 'dllexport' from deleted functions

[roubert]

https://groups.google.com/a/unicode.org/g/icu-support/c/61hEq3foH7o

Checklist

• Required: Issue filed: ICU-23247
• Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-NNNNN Fix xyz"
• Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-NNNNN Fix xyz"
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable
• Approver: Feel free to merge on my behalf

[markusicu]

wait

[markusicu]

@roubert we like your change, but we also think we should then cherry-pick it onto the maint/maint-78 branch. For that, please create a separate ticket, so that we can more cleanly mark that ticket for 78.2+79.1, and update this PR.

[jira-pull-request-webhook]

Hooray! The files in the branch are the same across the force-push. 😃

~ Your Friendly Jira-GitHub PR Checker Bot

[roubert]

For that, please create a separate ticket, so that we can more cleanly mark that ticket for 78.2+79.1, and update this PR.

https://unicode-org.atlassian.net/browse/ICU-23293

[markusicu]

Hi @roubert can you please cherry-pick this onto the maint/maint-78 branch? If not, I can ask @echeran to do so.

[roubert]

Hi @roubert can you please cherry-pick this onto the maint/maint-78 branch?

PR #3798