Fix failing tests on 6.x-dev [no_release]

[lachiebol]

Description

Issue: Matomo 6.0.0-b3 (matomo-org/matomo#24990) renamed the percent-of-total column titles from "(% of total)" to "(%)" and moved each one next to its metric in API.getProcessedReport, so the subtable expectation in TwoVisitsWithCustomVariablesTest no longer matched.

Fix: that expectation is now split by core version with an _old suffix for cores older than 6.0.0-b3. The unsuffixed file is regenerated for current core.

Automated fix for failing tests on 6.x-dev.

• Failing workflow: Plugin CustomVariables Tests
• Failing job(s): PluginTests (matomo6_max_php, maximum_supported_matomo, Mysql, 8.0), PluginTests (matomo6_min_php, maximum_supported_matomo, Mysql, 8.0), PluginTests (matomo6_max_php, maximum_supported_matomo, Mariadb, 10.6), PluginTests (matomo6_min_php, maximum_supported_matomo, Mariadb, 10.6)
• CI run: https://github.com/matomo-org/plugin-CustomVariables/actions/runs/36214548729

Generated by automated-test-fixes.

Issue No

Steps to Replicate the Issue

Checklist

• [✖] Tested locally or on demo2/demo3?
• [✔] New test case added/updated?
• [NA] Are all newly added texts included via translation?
• [NA] Are text sanitized properly? (Eg use of v-text v/s v-html for vue)
• [NA] Version bumped?
• [✔] I have understood, reviewed, and tested all AI outputs before use
• [✔] All AI instructions respect security, IP, and privacy rules
• [NA] Documentation updated?

[snake14]

LGTM