Set permissions for transaction files to 0o666

[eivindjahren]

Issue
Resolves #9794

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'pytest tests/ert/unit_tests -n auto -m "not integration_test"')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codspeed-hq]

CodSpeed Performance Report

Merging #9804 will not alter performance

_{Comparing eivindjahren:set_correct_permissions_for_transactioned_files (a1f044a) with main (a2fd3e1)}

Summary

✅ 24 untouched benchmarks