Allow users to start/stop notebooks when related image is deleted

[DaoDaoNoCode]

JIRA: RHOAIENG-14134

Description

Simply remove the detection of image availability to unblock users from starting with a deleted notebook image.

How Has This Been Tested?

1. Import a custom image in the settings page
2. Create a workbench with that image
3. Stop the workbench
4. Delete the custom image you created at step 1
5. Go back to the workbench list, and make sure you can still click the start button. (You will definitely get an error when starting, though)

Test Impact

Added a cypress test case to verify the button is enabled even when the notebook image is deleted.

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change.

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.02%. Comparing base (3b33b2e) to head (6c7b5cc).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3374      +/-   ##
==========================================
- Coverage   85.04%   85.02%   -0.03%     
==========================================
  Files        1329     1329              
  Lines       29930    29927       -3     
  Branches     8206     8204       -2     
==========================================
- Hits        25455    25445      -10     
- Misses       4475     4482       +7     

Files with missing lines	Coverage Δ
...rc/pages/projects/notebook/NotebookStateAction.tsx	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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[Gkrumbach07]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Gkrumbach07, jpuzz0

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