Truncate search suggestions similar to mediawiki.searchSuggest

The "containing..." entry at the bottom of the search suggestions
popup was not truncated like it is in the original MediaWiki
module, which is not used in Wikibase.

Additionally I moved the code a little bit to make it look like the
original code in mediawiki.searchSuggest.js.

Change-Id: If4a2893176067d723372b01fc0d35c3e7f760999
Merge "Truncate search suggestions similar to mediawiki.searchSuggest"