chore: disable line numbers in Confluence code blocks

[geopanther]

Summary

Disables line number rendering in Confluence code blocks for cleaner output.

Changes

• Modified Confluence renderer to set linenumbers parameter to 'false'
• Updated unit tests to expect 'false' value
• Updated functional test expected output (result.xml)
• Updated CHANGELOG

Testing

• All pre-commit hooks passed
• All pre-push hooks (including tox/tests) passed
• Tests updated to reflect new behavior

[geopanther]

Superseded by #77 after renaming branch to feat/configurable-code-linenumbers (conventional commit type corrected: chore -> feat, since this adds a new CLI flag). Closed automatically when the old head branch was deleted.