Fix mis-match condition in replacement question array

[marcellamaki]

Summary

Fixes #12335

References

Reviewer guidance

Are the proper number of replacements reflected in the replacement selection once you have added more than the current number of questions to swap?

https://github.com/learningequality/kolibri/assets/17235236/43185bb8-c66f-4da3-9a51-d2801f5f8fda

---

Testing checklist

• [ ] Contributor has fully tested the PR manually
• [ ] If there are any front-end changes, before/after screenshots are included
• [ ] Critical user journeys are covered by Gherkin stories
• [ ] Critical and brittle code paths are covered by unit tests

PR process

• [ ] PR has the correct target branch and milestone
• [ ] PR has 'needs review' or 'work-in-progress' label
• [ ] If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• [ ] If this is an important user-facing change, PR or related issue has a 'changelog' label
• [ ] If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions[bot]]

Build Artifacts

Asset type	Download link
PEX file	kolibri-.pex
Windows Installer (EXE)	kolibri-0.17.0a0.dev0+git.145.g5de86661-windows-setup-unsigned.exe
Debian Package	kolibri_0.17.0a0.dev0+git.145.g5de86661-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.17.0a0.dev0+git.145.g5de86661-0.4.2.dmg
Android Package (APK)	kolibri-0.17.0a0.dev0+git.145.g5de86661-0.1.3-debug.apk
TAR file	kolibri-0.17.0a0.dev0+git.145.g5de86661.tar.gz
WHL file	kolibri-0.17.0a0.dev0+git.145.g5de86661-py2.py3-none-any.whl