Minor fixes for lint:authors, lint:pretty code quality reports

Description

1. When make ... failed, the job was exiting immediately before writing the code quality report. Instead use make ... && status=0 || status=$? to save its exit status, write the report, and then exit ${status}.
2. Minor edits to common/maintainer-scripts/git_diff_to_code_quality_report to generate more compact JSON output.

I introduced some bad changes to lal/AUTHORS in a96ae3c2, which generated the following on the MR page:

The code quality report is also available here as part of the CI pipeline. (Note that, if the code quality report has a lot of changes, the widget on the MR page struggles to list them, but the report page from the CI pipeline appears more robust.)

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

Review Status

@adam-mercer @duncanmmacleod to approve.