fix(engine): remove extra unnecessary delete

[npepinpe]

Description

This PR removes an extra deleteExisting which breaks inconsistency checks.

Definition of Done

Not all items need to be done depending on the issue and the pull request.

Code changes:

• The changes are backwards compatibility with previous versions
• If it fixes a bug then PRs are created to backport the fix to the last two minor versions. You can trigger a backport by assigning labels (e.g. backport stable/1.3) to the PR, in case that fails you need to create backports manually.

Testing:

• There are unit/integration tests that verify all acceptance criterias of the issue
• New tests are written to ensure backwards compatibility with further versions
• The behavior is tested manually
• The change has been verified by a QA run
• The impact of the changes is verified by a benchmark

Documentation:

• The documentation is updated (e.g. BPMN reference, configuration, examples, get-started guides, etc.)
• If the PR changes how BPMN processes are validated (e.g. support new BPMN element) then the Camunda modeling team should be informed to adjust the BPMN linting.

Other teams:
If the change impacts another team an issue has been created for this team, explaining what they need to do to support this change.

• Operate
• Tasklist
• Web Modeler
• Desktop Modeler
• Optimize

Please refer to our review guidelines.

[lenaschoenburg]

😬