Handle Org titles containing abbreviations

Ensure that we avoid a situation where the ``abbr`` tag has a title (ie tooltip) which includes the abbreviation. For example, this could have happened:
"WO" => "Wales Office (WO)"

Whereas we always want:
"WO" => "Wales Office"

This lets us change the way that Rummager returns Organisation titles so that it does less work.

Regex code copied from:
https://github.com/alphagov/rummager/blob/297e586de331c6830db07854d1ac55456684f100/lib/organisation_registry.rb#L48-L67