Close language modal when language not changed

[MisRob]

Summary

Close language dialog and do not send a request when a language not changed.

Reviewer guidance

1. Open Change language modal (can be opened from app bar menu, signin page footer or during setup wizard)
2. Do not change language selection
3. Click Confirm

References

Closes #7067

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Contributor Checklist

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

Testing:

• 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

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

[codecov]

Codecov Report

Merging #7231 into release-v0.14.x will decrease coverage by 0.01%.
The diff coverage is 0.00%.

Impacted Files	Coverage Δ
.../views/language-switcher/LanguageSwitcherModal.vue	23.52% <0.00%> (-9.81%)	⬇️
kolibri/core/content/utils/check_schema_db.py	91.30% <0.00%> (-8.70%)	⬇️
.../core/deviceadmin/management/commands/dbrestore.py	76.56% <0.00%> (ø)