Code-format accepted values, not identifiers, in the config reference

[JeroenDeDauw]

On the MediaWiki:Maps reference table, the Setting and LocalSettings.php columns no longer wrap their identifier in inline code (it was the whole cell, so it distinguished nothing). The Accepted value column now renders its literal tokens as code — true/false, units, enum values, language codes, auto — while descriptive text such as "0 or greater" stays plain.

_{AI-authored — Claude Code, Opus 4.8 (1M context) (max); request from @JeroenDeDauw, no revisions; diff not yet human-reviewed; Config unit + integration suites green locally and the rendered table eyeballed on the dev wiki, phpcs clean, CI pending.}