Hide "Delete dashboard" button for default dashboard

[johannaengland]

Dependent on #3233. Another potential part of the fix for #3150.

This hides the "Delete dashboard" button for the default dashboard. Up for discussion if this is how we want to prevent the user from trying to delete the default dashboard.

But this is how it is done for the case where the current dashboard is the last dashboard.

Before:

After:

[github-actions[bot]]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	black	992		0	12.77s
✅ PYTHON	ruff	988		0	0.1s

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[github-actions[bot]]

Test results

    9 files      9 suites   8m 20s ⏱️ 2 143 tests 2 143 ✅ 0 💤 0 ❌ 4 025 runs  4 025 ✅ 0 💤 0 ❌

Results for commit 2a3fe465.

:recycle: This comment has been updated with latest results.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 60.30%. Comparing base (855819a) to head (2a3fe46). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3234 +/- ## ======================================= Coverage 60.30% 60.30% ======================================= Files 605 605 Lines 43685 43685 Branches 48 48 ======================================= Hits 26343 26343 Misses 17330 17330 Partials 12 12 ```

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[johannaengland]

Discovered one problem: If you are in the settings for a dashboard that can be deleted (so the button is shown), then you change it to become the default dashboard, then the delete button is still there and can be clicked

Ooof, that means I have to look at the javascript code again :sweat_smile:

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud