Bump drupal-rector to beta version
### Problem/Motivation
Update the drupal-rector dependency constraint to target a beta release version.
### Work items
- Commit(s): [121ddc618f](https://git.drupalcode.org/project/project_analysis/-/commit/121ddc618f0e), [34e88727c1](https://git.drupalcode.org/project/project_analysis/-/commit/34e88727c1a9)
### Credit
- Implemented by: @bbrala
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*Filed retroactively as part of the Drupal 12 rector coverage effort. Closed as fixed; credit to be applied to the contributors listed above.*
*AI was used extensively to build this work and to file this issue. See [Dries Buytaert: AI-generated Rector rules for Drupal](https://dri.es/ai-generated-rector-rules-for-drupal) and [Björn Brala: Drupal Rector rules are config, not code. Mostly.](https://www.linkedin.com/pulse/drupal-rector-rules-config-code-mostly-bj%C3%B6rn-brala-vfpwe/).*
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