Delete connection ref from notebooks when connection is deleted

[jeff-phillips-18]

Closes RHOAIENG-14208

Description

When removing a connection, delete the env var from the env var list of any connected notebooks

How Has This Been Tested?

Delete a connection that has connected notebooks
Go to the workbenches tab and edit the notebooks that were connected.
Verify the connection is no longer listed in the Connections section

Request review criteria:

• 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)

[christianvogt]

/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: christianvogt

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• frontend/OWNERS [christianvogt]

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[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 85.94%. Comparing base (217787a) to head (b90f76e).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...eens/detail/connections/ConnectionsDeleteModal.tsx	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3428   +/-   ##
=======================================
  Coverage   85.93%   85.94%           
=======================================
  Files        1339     1339           
  Lines       30308    30311    +3     
  Branches     8367     8369    +2     
=======================================
+ Hits        26046    26050    +4     
+ Misses       4262     4261    -1     

Files with missing lines	Coverage Δ
.../screens/detail/connections/ConnectedResources.tsx	91.66% <100.00%> (ø)
...ts/screens/detail/connections/ConnectionsTable.tsx	100.00% <ø> (ø)
...eens/detail/connections/ConnectionsDeleteModal.tsx	82.97% <80.00%> (-1.12%)	⬇️

... and 7 files with indirect coverage changes

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