Fix Guacamole copy/paste configuration

[JimMadge]

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⤴️ Summary

🌂 Related issues

🔬 Tests

Tested on a fresh deployment. Unable to copy/paste to/from local machine and workspace.

[github-actions]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
data_safe_haven/external/interface
azure_postgresql_database.py					145-146
Project Total

This report was generated by python-coverage-comment-action

[craddm]

Confirmed that the connection settings in guacamole now show appropriate configuration:

Testing shows that the user can be no longer copy or paste into or out of the workspace, but can copy and paste within it (e.g. from one terminal window to another)