ICU-22220 BRS73RC Update version number and regenerate configure v73.1

[rp9-next]

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22220
• Required: The PR title must be prefixed with a JIRA Issue number.
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number.
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[jira-pull-request-webhook]

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

~ Your Friendly Jira-GitHub PR Checker Bot

[pedberg-icu]

Looks good, thanks!

[markusicu]

lgtm tnx

@rp9-next did you check if the .jar files actually have meaningful changes (other than differences in zip compression)?

[rp9-next]

The last time we checked, while two of the JAR files were exactly same (apart from the "Created By" changes in the MANIFEST.MF)
I believe there were changes with respect to the version number encoded in "*.cnv" and some other changes in ".res" files in testdata.jar