Remove unused max_plugin_runtime configuration variable

[Donnype]

Changes

This is an artifact from #1187

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Code Checklist

• All the commits in this PR are properly PGP-signed and verified;
• This PR only contains functionality relevant to the issue; tickets have been created for newly discovered issues.
• I have written unit tests for the changes or fixes I made.
• For any non-trivial functionality, I have added integration and/or end-to-end tests.
• I have performed a self-review of my code and refactored it to the best of my abilities.

Communication

• I have informed others of any required .env changes files if required and changed the .env-dist accordingly.
• I have made corresponding changes to the documentation, if necessary.

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Checklist for code reviewers:

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Checklist for QA:

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