mediawiki.util: Fix jsduck syntax and minor clean up

mediawiki.util: Fix jsduck syntax and minor clean up

* Fix indentation of @param comment to not trigger <pre> context.
* Clean up descriptions.
* Apply coding conventions
  - Function call one one line, or one line per argument.
    Avoid arbitrary splitting mid-line when purely for the sake
    of line length.
* Combine string concatenation in one expression instead of
  adding twice.

Change-Id: Id9f2a7cef1c8bf1c01584fbb293d0605fc91337e