Check for select value and label prevents valid select from repeat patterns

Some time between July 2023 and February 2025, [this form with a select from repeat](https://docs.google.com/spreadsheets/d/1K9I-nbdn1g_YYyiG_IuQW-YhtcODG9IPmQA2qRKsds8/edit?gid=0#gid=0) stopped passing Validate. When I convert it to XForm with `--skip_validate`, it works as expected in Collect. We have tests in JavaRosa for this form shape. Was there a change in pyxform? Validate? Could we remove that check since pyxform does that work already?

Start with the linked form and the existing JavaRosa tests for this repeat/select shape, then compare Validate behavior with `--skip_validate` and Collect. Review changes in pyxform and Validate between July 2023 and February 2025; done means identifying the regression and confirming whether removing the duplicate check restores valid forms without weakening required validation.

Written by the indexing model from the issue text.