Remove some legacy things from the locale fallback file

[sffc]

Part of CLDR-16253

In an effort to migrate the ICU-specific aliases upstream to CLDR (https://github.com/unicode-org/cldr/pull/2664), I wanted to remove some aliases that were labeled legacy or similar in ICU. I don't entirely know the impact of this change so would appreciate a review from that angle.

Checklist

• [ ] Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-_____
• [ ] 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

[macchiati]

Are you going to try to finish this in this version of ICU?