Bump Blueprint; remove obsolete hotfixes, deprecations

[RichDom2185]

Description

Based on Blueprint's v5 changelog, from v5.9.0 onwards, we will have no more React 18 warnings, thus the hotfixes introduced in #2504 are no longer necessary.

Also, the popover2 package is no longer required since it just reexports the new components.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [x] Code quality improvements

How to test

Checklist

• [x] I have tested this code
• [ ] I have updated the documentation