fix(server): ignore removed experiments during name uniqueness check

[xnaveenx]

Fixes #4336
Proposed changes
This PR fixes a bug where updating an experiment would fail with a "Duplicate Name" error if a deleted experiment existed with the same name.

Changes:

Modified the database query in the UpdateChaosExperiment handler.

Added a filter to exclude experiments where is_removed: true (or deleted_at is not null) during the name uniqueness check.

Types of changes
[ ] New feature (non-breaking change which adds functionality)

[x] Bugfix (non-breaking change which fixes an issue)

[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

[ ] Documentation Update (if none of the other choices applies)

Checklist
[x] I have read the CONTRIBUTING doc

[x] I have signed the commit for DCO to be passed.

[x] Lint and unit tests pass locally with my changes

[x] I have added tests that prove my fix is effective or that my feature works (if appropriate)

[ ] I have added necessary documentation (if appropriate)

Dependency
None

Special notes for reviewer:
Verification (The "Ghost Test"): I verified this locally on a K8s cluster:

Created an experiment named Ghost-Test.

Deleted Ghost-Test.

Created a new experiment named Ghost-Test (this worked previously).

The Fix: Successfully updated the new Ghost-Test (added tags/description). Before this fix, this step failed with a duplicate error.