Fix missing close of hg diff command

[sdorra]

Proposed changes

The mercurial diff resource does not close the command context, which leads to an open python process which gets never closed.

Your checklist for this pull request

• PR is well described
• Related issues linked to PR if existing and labels set
• Target branch is not master (in most cases develop should bet the target of choice)
• Code does not conflict with target branch
• New code is covered with unit tests
• CHANGELOG.md updated
• Definition of Done's fulfilled: DoD // UI DoD
• Documentation updated (only necessary for new features or changed behaviour)

Checklist for branch merge request (not required for forks)

• Branch is green/blue on Jenkins
• Quality Gate passed on SonarQube

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

90.0% Coverage
0.0% Duplication