Update search-ui.js : typo in query config

[awoods]

The intent of the code is to perform an AND query with the terms provided in the search. However, there is a typo in the search fields configuration that results in the default OR behavior. We should be using bool: "AND" instead of 'boolean: "AND"'.

See: https://github.com/weixsong/elasticlunr.js#522-boolean-model

To test on the demo site:

• a search with "portrait" returns 3 results.
• a search with "portrait Majnun" currently returns 4 results (OR behavior)
• the search should return 1 result (AND behavior)

[mnyrop]

thanks @awoods!